To add to everything else said, you should usually try to avoid direct space combat confrontations with the Empire early on. Your capital ships simply aren't very good against other capital ships so the only way to deal with Victory or Imperial Star Destroyers are with your fighters since they're far superior to tie fighters which are the only fighter the Empire starts out with. The only thing you should be building with your shipyards in the early stages of the game are X-Wings. That's it, nothing else, just crank out X-Wings like crazy and use your fighter compliments to defend only your really important systems (any planet you have with a construction yard is generally most important, followed closely by planets with shipyards). Also protecting shipyards is important in the early game since you need those X-Wings for additional protection and a place for Wedge to start ship design research right away. Also remember to win as the Rebels you likely aren't going to win the game anytime soon, it's a war of attrition and the longer the game goes along the more likely things are going to be in your favor as the Rebels. Building up your infrastructure with a bunch of construction yards where you start with them and using diplomacy on planets which have production facilities will benefit you a lot so by day 100 you'll be likely to have yourself a bit of production going and some defenses established.
For playing against the AI you'll generally utilize different strategies or tactics to deal with their tendencies and how generally dumb it can be with their resources and ships, multiplayer is a much different ballgame and requires much more use of espionage to keep an eye on an opponent which is far more unpredictable than a crummy AI in single player. As the Rebels, you'll have to take calculated risks and roll with whatever results from that. Like sending characters on missions even if there's a bit of a garrison there cus you have to cause damage to the Empire in whatever way you can to set them back, or trying to sabotage a capital ship that has an admiral on board making it more likely they'll foil the mission or capture someone trying to sabotage. As the Rebels that's just how life goes.
In the beginning, it's possible you'll lose a planet to the Empire, possibly more especially if you have any planets that start out in the same system as Coruscant (usually you'll end up losing those planets fairly fast which is a stinker if they have production facilities, but that's how the game goes with random spawns). Note that only things that aren't randomized are Coruscant and Yavin and how those planets start out, outside of starting resources and facilities on those planets which are randomized for every planet in the game.
For your characters on Yavin, have Han use his Millenium Falcon mode of travel (travel time is cut in half essentially) to get him and all the other characters into the core systems as soon as possible, for things like diplomacy, recruiting, sabotage/espionage if there are Imperial planets nearby, and ship design research for Wedge. Note that special forces such as bothan spies or infiltrators can't come along for you to still receive the Millenium Falcon bonus, only characters. This ability Han has with the Millenium Falcon also applies to things like missions as well, travelling time to a planet or location you're doing a mission at is halved providing you're not using special forces like spies or infiltrators. This ability of Han is really useful for carting around important characters as well or traveling distances with him and other characters where they may be more useful and doing so in less time than traveling on a fleet.
One thing to note about Luke, whenever a mission of his gets foiled, he'll become stronger in the force and his force rating (in the hidden arbitrary number coding wise) will become marginally better. So sometimes sending him on a mission he's likely to fail but not very likely to get capture can be good for him to raise his force rating and improve his skills at a somewhat better rate than if he had succeeded. As the Alliance though you'll have to choose between recruiting and other missions for Han, Leia, and Luke at the beginning as they have multiple uses.
Generally at the start, your headquarters will be plenty safe unless it's reasonably close to Coruscant somehow. If it's on the right and/or bottom portions of the map, then you probably don't have to keep a heavy garrison there since the Empire (at least AI, for human opponents it may vary) will probably not find your hidden base for a very long time, so keeping a heavy garrison there is a moot point if the Empire doesn't even know where it is and likely won't know for a 100 days or longer. It's better to send your fighters somewhere more important in the core systems to protect an important planet, since your fighters are the best early game defense you have. Your troops unlike the imperials will be best used as garrisons to prevent sabotage/espionage missions from succeeding, and to use them in settling out rim planets. There's a trick you can use with your Headquarters to settle outer rim planets quickly and isn't too risky if there isn't much of an Imperial presence in the nearby systems. If you have a medium transport at your headquarters to start, you can plop down a troop regiment on an unsettled planet, then move your headquarters there which will give it a full support bar. This eliminates the need to have to build a facility on the planet to gain a support bar (allowing you to move the troop garrison elsewhere to settle another planet or do something else), which takes a long time to get to since you need plenty of construction yards to do that. When your headquarters leaves a planet which has a full support bar, it'll only go down a tiny bit meaning you don't have to worry about losing any planets using this trick. It's kind of cheesy and can be a bit risky against human opponents who tend to scout the out rim a bit more aggressively, but it's generally well worth it to at least do it in the same system your headquarters is in since it's the only planet the Rebels start with which is guaranteed to have a construction yard.
Using sabotage missions on things like production facilities or capital ships generally causes your opponent to be set back much more in the early game than in the mid or late game, so doing those early and often if possible is one thing you should focus and keep an eye on. It's harder to replenish or replace losses like those in the early game than it is later, like if planet were to have only 2 construction yards and you sabotage one it'll take much longer to replace that one than if a planet had say, 7 or 8 construction yards already established. Losing capital ships early in the game means that they won't be able to be replaced for at least several hundred says, since a player would have to build up an infrastructure of construction yards, then use those to build up a compliment of shipyards at a planet (or two), then patiently wait as those shipyards are shipped to whatever planet you're using as a shipyard center, then when you have enough shipyards there take the time to build a capital ship or two (and victory/imperial star destroyers are very expensive to build and take a long time, those are irreplacable ships in the early game). So while sabotaging things like mines and refineries in the early game is still a decent option, generally in muliplayer games each player doesn't start with enough manpower to have any problems with maintenance points so it would take awhile for the sabotage to add up to the point it effects your opponents plans. Speaking of missions, using capital ships as a hub for characters to perform missions (especially in systems where you don't control a planet) is essential. Just remember it's possible for your opponent to run missions on you as well, and if they run successful espionage missions they can know what you're up to. A smart player will also figure out if you are using a ship as a hub for your characters to perform missions (especially if you succeed in a mission or two your cover will be blown, so pick the more important targets first) and will possibly send in a ship to neutral planets drive it out of the system, so be wary of that possibility and stay mobile with your capital ship if you can once your character(s) return from doing a mission. Even if a ship like a Bulk Cruiser has little use in combat as they can only really take on Carrack Cruisers head to head (in terms of combat ships), they can still be useful as ships to provide a hub for characters to go on missions or move into a different system (Han is the only character who can travel faster than capital ships between planets/systems, so using extra capital ships for characters to travel around saves time). You have to get any use you can of the resources provided so you just have to improvise and realize even your capital ships will usually be used on the defensive or as a way to cart characters around. As the alliance having one or two ships (usually transports) exploring the outer rim isn't a bad idea, though it generally only pays off to settle a good deal of outer rim planets for longer games in bigger galaxy sizes.
Post edited January 25, 2015 by thelovebat