Usually in colonization mode, I use the divide and conquer strategy.  I get the strongest races fighting each other and strike when they are weakened. I also rely on a surprise attack on a homeworld to weaken an opponent quickly.   This lets me build up my infrastructure when they are fighting.

In campaign mode, when you have only one opponent and he starts off at war with you, this option isn't available.  Any tips on strategies that work well in this situation ?  Go straight for planetary conquest and weapons ?

Also:  I noticed that in Dark Avatar, my core ships aren't upgrading themselves the way they did in TA.  I could fit 4 lasers on a tiny ship and my Star Fury was still being build with 1 laser.  Is there an option that must be set to auto-upgrade the core designs ?   When I noticed this, I manually designed a tiny ship that could fit what weaponry it could hold given my miniaturization and weapons tech.  (This was in Campaign mode).