At the start of a new campaign, build lots of Mining Facilities on each planet. They can be sold later if desired. Have the droids steal Imperial technology immediately from the start. It is sufficient to build Factories, Barracks, etc. on only a few of planets to begin with, as forces can easily be moved to the desired location after they have been produced. Instead of having ground forces protecting your planets, concentrate on building a large fleet for each planet. Make sure your Space Station is upgraded to the maximum at all times. This should be sufficient to repel the Imperial fleet and thus prevent a ground assault altogether. You will also need to build a large separate attack fleet in order to conquer planets, as you cannot leave any of your planets unguarded at any time. Also, make sure Antilles' ship is included as his "weaken enemy" special attack is extremely effective. Place all your ground forces into one huge army following your attack fleet around the galaxy, but never put them in the same fleet. A surprise attack could leave your transport ships facing a Star Destroyer. Make sure you have bomber squads in your fleet to allow for bombing raids on planetary battles. Bring the droids as well, as they do not affect the total number of units allowed, and their ability to repair units can be very useful if there are no building pads nearby. As soon as you have conquered a new planet, build a fleet to protect it. Do not remove your main fleet until the the planetary fleet is in place, or you will risk being attacked immediately. As the game progresses, the Imperial fleets will grow bigger; make sure your attack fleet and planetary defense fleets are up to strength, and do not forget to replace losses immediately after a battle.