Tips and Tricks
Staking your claim
The game will almost always start with you in a star system with a few other players. While the first few minutes of the game will usually be relatively leisurely, you're soon going to run out of space to expand. Unless you happen to be playing with unlocked teams and can ally with your neighbors and live in cramped conditions, expanding more is almost always a better idea. Especially in 1v1, fast initial expansion is often one of the most important keys to winning: acquiring territory close to the enemy, building a fleet, and preventing the enemy from expanding further is extremely important. Having a couple of frigate factories and a couple of repair platforms on your front lines is a good start: the repair platforms can repair each other and the factories if needed, and your factories can quickly build a fleet to fight your opponent. Constantly be scouting out your opponent(s): be aware of their fleet's general location at all times, be prepared to fleet up to defend if they come close, or go on the offensive if they're out of position!
On smaller maps, there are often gravity wells that have only one or two phase lane entrances from the direction of the enemy, gravity wells which the enemy must go through to get to you. Securing key choke points like these is very useful: it's easier and cheaper to be able to defend a single choke point than (for instance) be having to attempt to defend 2 adjacent planets. If you see a choke point you can capture, beeline for it, especially if you have a colonizer capital ship, and once the planet is yours, consider significantly fortifying the choke point. A defending fleet, a starbase, a phase jump inhibitor or two, repair platforms, and frigate factories could work wonders at a choke point.
Stars and wormholes can also be used as chokepoints, you can read more about it a bit down.
Since Diplomacy Pirate Raiders have become much harder. Read the section "The Above is not longer true" at the bottom of this Pirate Raiders discription for updated info. Basically, pre-Dipomacy the pirates are not that hard and they are useful for experiance but in Diplomacy they get harder and harder each wave until they are the most powerful faction in the game.
Early in the game, pirate raiders will slow your expansion and development, but any capital ship in the gravity well while you're fighting off pirates will gain a significant number of experience points, which are very useful. Putting bounty on enemy players will slow their expansion down for a while in the early-game, but especially against the harder AIs, it can be tough economically to continually finance bounty on enemies until the pirates are launched.
If pirate raiders are launched against you, don't panic! They will attack the closest planet to the Pirate base that they consider to be a significant enough target - for instance, they would probably skip over an empty Dead Asteroid of yours close to the Pirate Base and instead move on to that heavily built-up Desert planet you have closer to the center of your empire. Although they come in massive numbers, pirates are usually easily defeated with a starbase or a capital ship with a couple of repair platforms and a few turrets to support.
The Pirate base can be a nuisance if it's located at a key choke point or if your trade ships travel through them. Very occasionally in the late-game it's worth it to completely destroy the pirates in order to secure the planet, but only if you and your opponent(s) are completely deadlocked on opposite sides of the Pirate Base and have no other way of reaching each other. It is actually quite simple to navigate a large battle fleet through the Pirate base without taking any losses: send a scout ship in first and order it to circle the gravity well, outside of the range of the turrets. Once the pirate ships start chasing your scout, you can warp in the rest of your fleet and have them form up and jump to your destination at your leisure, as the pirates futilely pursue your agile scout. For this reason, it's rarely necessary to take the time and money necessary to destroy the pirates. Wiping out the Pirate base is somewhat expensive and extremely time-consuming, but very doable if you have a fleet with lots of carriers. Once you have a fleet supporting 40+ bomber squadrons (which is relatively common late-game), first send in the usual scout ship or two to fly around and distract the pirates. Then, bring your carriers in, and watch as their bombers decimate the pirates. It will probably take a long time since there are so many pirate units to destroy, but is easy to do with minimal losses. It's important to make sure the distraction scout is constantly circling the edge of the gravity well, though: if it's destroyed, the pirates will move on to attack your carriers and you'll be forced to retreat (or your ships will be destroyed).
As of diplomacy or one of the later patches, pirates are now much tougher to take down. The pirate turrets now have incredible range (outranging the TEC and Advent anti-structure cruisers) and retaliate against fighters and bombers (the bombers and fighters seem to be dealt damage equal to the damage they give to the turrets, and considering turrets have over 3000 hitpoints.......). This makes pirates tough to defeat. The most effective method, if playing as TEC, is to use the Novalith Cannon to destroy the planet. Of course, this will not clear the gravity well of the annoyingly powerful ships nor the ridiculously powerful turrets. As of Rebellion, it is not uncommon to use a titan class ship to attack the pirate base for the sole purpose of gaining experience for the titan.
Dead end planets
Dead end planets (planets that appear at the end of a phase line with no other phase line leading to them) can be very useful in your conquest. All available planets are useful, but enemies are not likely to stumble upon these types of planets, so they can be colonized without you having to worry too much about them. That is not to say they will not be attacked, but attacks are less likely and more easily prevented. However, especially in the early-game, your priority should be advancing your fleet towards the enemy and taking planets along the way. Once your front line is established and you have the spare resources, dead end planets should then be colonized.
Dead end planets are also often great spots for superweapons if they're far away from the front lines.
Damage and armor types
Different units in Sins of a Solar Empire do different levels of damage to different units, depending on the armor of the defending unit and the damage type of the attacking unit.
This is only a short summary of the effectiveness of a few ships against others. To look at the raw numbers, damage and armor types, the easiest way would be to look at the spreadsheet pages provided by a helpful user on the Sins forums:
A good player will know this chart pretty well - memorizing it is not essential, but it is very useful for understanding what units counter what. Being able to quickly analyze an enemy fleet and queue the appropriate units to effectively counter them is the core of a good Sins player.
Against the AI and pirates, defense platforms (turrets) can be very useful. They are relatively cheap, do quite a lot of damage, and have relatively large amounts of armor and hull. When you have a lot of turrets that are supported by repair platforms, they can defend against a significantly more costly enemy fleet - the only problem is that enemy Assailants, LRM frigates, and carriers will outrange the turrets and will eventually destroy them unless you send in a moderate fleet to help defend. Combined with an upgraded starbase, this will make a planet virtually impenetrable - against the AI. Human players will simply evade turrets and destroy them once they have the freedom to. In general, static defenses are much more useful against the AI than against humans - but when strategically placed, a few turrets can still be useful in multiplayer games. The problem with using static defenses against humans is that they can be evaded relatively easily, and will then turn into casualties if the enemy manages to push your fleet back. Against human opponents, it is almost always better to build up a fleet (which can retreat, and can move to fight anywhere) rather than to fortify with static defenses. However, when building defenses, it's a good idea to place all the structures relatively close together so they can defend each other most effectively.
In general, it is cheaper, easier, and faster to install a turret rather than a hangar. Although one may be tempted to build a Hangar Defense or few, it is relatively easy for the enemy to negate its firepower, either by using flak or fighters. Unless you are Vasari, if you're focused on building static defenses, it's generally a better idea to invest in turrets than hangars. However, Vasari hangars can be upgraded via research to have the fearsome Phasic Trap ability, which can freeze vast numbers of enemy strike-craft and render them harmless almost indefinitely. This is a very effective strategy, even against human opponents. As Vasari, having a few hangars with Phasic Trap near a starbase on a key world can completely negate carrier-based enemy fleets. The other races are usually better off defending with turrets (or a fleet).
Phase jump inhibitors
Phase Jump Inhibitors (PJIs) are expensive, but are one of the greatest tools to destroy an enemy fleet attempting to retreat. Phase jump inhibitors greatly slow down the rate at which enemy ships charge up their phase drive: a fleet attempting to retreat while taking 40 seconds or more to warp out (due to PJIs) will take very heavy losses when being attacked by a fleet of comparable size defending the planet. For this reason, if you are attacking a planet and see a PJI on it, you should probably focus-fire on it first with your good anti-structure units (Ogrovs, bombers, HCs, possibly LRF), else you risk possibly being forced to retreat and have your fleet wiped out by the enemy. The Vasari, with their moving starbase, are especially fearsome defending a planet when combined with a PJI or two, because the starbase can move towards the enemy fleet, wherever it is in the gravity well, and do horrendous amounts of damage to it while it is attempting to retreat.
Wormholes and stars
If you control planets surrounding a wormhole or the star, it's a good idea to have a scout or two sitting in the gravity well as it gives a bit of a early warning if enemies are attacking through those points and can alert you to the need to move (or build) a retaliation fleet ready to push them back.
Leaving a scout at every uncolonizable gravity well close to your borders as an early warning system is always a good idea. If the first you hear about an attacking enemy is shots being fired at one of your planets, it's probably too late...
If you are playing a larger map with multiple star systems it can be difficult to defend all of your systems. One bold tactic is to go with your fleet to the enemys star. Find out where they come in at the stars gravity-well and then you deploy starbases there. While they are building your fleet will protect them. Now you only have to focus on one star system. Later on you could bring capital ships and titans for supportive xp farming.
The power of money
Veteran players of games like Starcraft know that economic warfare can be just as important as the number of units on the battlefield. Destroying the enemy's fleet is one thing, but crippling their income rate or their ability to build more of their fleet can be just as effective. Killing enemy frigate factories may not do anything about the fleet parked on your doorstep, but it ensures that every unit you kill will not be replaced soon after. Destroying enemy trade ports will also significantly decrease your enemy's ability to build ships. If you can manage it, economic warfare can be a key part of winning a war of attrition. Conversely, investing in a robust economy along with a good defensive fleet is a good way to mitigate the effects of economic warfare.
Tips for building a successful economy:
Note: The TEC easily has the best economy out of all the factions. As such, the longer the game goes on, the higher the chances are the TEC will win, as their high defenses and very good economy means that they will always win a war of attrition. If you're fighting a good TEC player and the game starts dragging on, you better start some economic warfare quick before he swamps you with seemingly endless fleets being supplied by his superior economy.
If the enemy fleet is busy fighting your own, and if you can, use Ogrovs, siege frigates, and carriers with bombers to bypass the enemy's front lines and destroy their planets and infrastructure! If your main combat fleet can stand on its own defending against the enemy fleet, and you have spare funds and fleet supply, then a vicious tactic is to then build 8-12 siege frigates and/or a similar number of Ogrovs, or carriers with bombers if you can manage it. The perfect time to attack with them is if the enemy sends their fleet to one of your own worlds: while your own fleet defends your planet, send your siege frigates and/or other raiders to enemy planets. Although you can attempt to target the enemy's front-line planet(s), due to their fortification, often it's a good idea to warp into an enemy's adjacent planet and attack the planet or structures there. If you two are primarily fighting over a single choke point (one or two phase lanes) but there are other undefended routes to other enemy planets which aren't being used, use those other phase lanes instead, because it will take a lot of time for your opponent to retreat his fleet and move it to defend those more distant planets. While (if) your opponent retreats his fleet to defend those worlds, your combat-oriented fleet will be free to pursue his fleet and pick off the retreating ships, and then to attack the front-line planet. Using this strategy can completely wipe out a few enemy planets and will absolutely decimate the enemy's infrastructure, depending on the distance from the enemy's combat fleet to your raiding forces: however, make sure to attempt to retreat your raiding forces if a significant enemy fleet arrives, because your raiding ships are both expensive and fragile. Still, a successful use of this strategy can easily win you the game in a 1v1.
The Novalith Cannon is the very powerful TEC superweapon that can wipe out planets and asteroids in one or two shots. If you are otherwise deadlocked with your opponent(s) and have a whole lot of spare resources, it's not a bad idea to research and build a few Novaliths. They can bombard planets from afar and wipe out the enemy's empire while your fleet can stay guarding your own planets. The problem is that the Novalith Cannon is very expensive to research and build; if you are playing the AI and can afford it, go for it, but against humans, it's generally not worth it, for a number of reasons. Although the first cannon shell will most likely wipe out the target planet, the player can simply recolonize it a few minutes later; in addition, a decent player will then start building starbases on their important worlds and upgrade the starbases to prevent planet loss due to bombardment. This will mostly negate whatever Novaliths you build. The sheer amount of funds required to build Novaliths in the first place is also very prohibitive: if you're researching Novaliths instead of investing in your fleet, a decent human enemy will simply fleet up with the funds they have, annihilate your significantly inferior fleet, and start wiping out your planets. That said, Novaliths can be useful late-game if enemies are refusing to surrender and you have lots of spare resources to research and build the superweapon.
The Kostura Cannon is the Vasari superweapon. While it is not, in of itself, a game winner, it can significantly help your fleet attack the enemy; generally, players fortify their front line planets while mostly neglecting building defenses on their core worlds. The Kostura, however, upsets this strategy. A Kostura shell makes its target planet a temporary Phase Stabilizer Node, which you can travel to directly instead of having to use the intervening phase lanes (if your fleet travels from a Phase Stabilizer Node of its own). If you have your fleet on one of your own planets with a Phase Stabilizer, you can fire the cannon at a core enemy world, warp your fleet in directly to the enemy planet, and wreak havoc while the enemy fleet is busy attempting to travel along the long phase lanes back to the core planet you're attacking. Even if the enemy fleet is stronger than your own and eventually engages yours, you can flee back to your original planet without taking losses if you have a level 6 Antorak Marauder with Stabilize Phase Space. This is exceptionally useful for taking out enemy superweapons or for wiping out the enemy homeworld with a large number of siege frigates. While the Kostura Cannon does a moderate amount of damage against enemy structures on the targeted planet, you will need a large number of Kosturas to completely destroy the enemy structures, especially if they have any hull or armor upgrades. Given their cost, it's rarely worth it to build more than 2 or 3 Kosturas.
The Deliverance Engine is the Advent superweapon. When its target is hit, it causes a sharp spread of your culture that often travels down several phaselanes. This has several notable effects.
Using Eyes of the Converted research it will unveil groups of enemy planets. This can be used to update backline information quickly in preparation for an attack.
Hitting a planet, or chain of planets/chokepoint, you are about to attack will have all of your ships fighting 'under the inluence of your culture' and enemy ships without their culture benifits.
Firing it at the enemy's economic center will reduce their planetary approval rating and thus their income.
Shooting a planet consistantly will eventually cause it to go neutral and be unclaimable by anyone but you. For populated planets this takes a fair ammount of time and more than one cannon, making it a less viable tactic. This effect does have several uses, however. If you fire it in preparation for a push into enemy territory they will be unable to recolonize the planets you took for quite a while. This can also work in reverse on your own planets. You can fire it on your front lines to keep your ships 'in culture' and to prevent the enemy from taking and fortifying planets that fall. If you find yourself spread out, you can hit your distant planets for a quick morale/income boost, though you are better off using the above offensive tactics.
When you are playing against the AI with multiple systems and you have conquered the entire current system, you want to hold on to all that territory. The best way to do that is to build starbases in wormhole gravity wells (if present) and 4 starbases in the star's gravity well. On the star, maxing out on all hangar upgrades for all 4 starbases will make it very difficult for any fleet to attack your star system without taking very heavy losses - but don't forget to have a few repair ships near the starbases as well, in case they get damaged!
While the above is a valid strategy for playing against the AI, the massive amounts of resources necessary would almost always be much better invested in other things when playing against humans, such as an offensive fleet.