It depends. In other RTS games, I usually did a few small scouting rushes, and made a decently sized force and attacked with a portion of them, then drew out a few foes and had my larger group deal with them. I'll also usually just use cheap and quick-to-make forces for the majority of the game, possibly upgrading to higher level guys, but ones that are still cheap and stuff. Kinda like from zergling swarms to hydralisk swarms. ^_^ Airborne guys are great too. Of course, with EAW, well, I don't know enough of how it works and stuff to make a strategy, but my experiences with other RTS games will basically be my outline. Can't wait for the demo.
I'll make a decision about getting the full game (if my PC can perform decently with it) from the demo stuff.