I favourite tactic of mine is to rush build a military Starbase, next to planets I'm going to invade. I stockpile some Constructors, check what weapons/defence the enemy has, and then build the Starbase to assist my invasion fleet. This can be a big help. in the early game. Esp. as the AI seems to concentrate on one weapon/defence tech.
I think this is a bit cheesey and perhaps the building of Starbases modules needs to be slowed down a bit and the building of these next to AI plane triggers a negative response?
Although, the AI does now seems more aggressive in attacking these starbases once your at war.
Do other people use this tactic?