[Suicide Junkie]

Well, the first thing to do is analyse the enemy designs.
Figure out why they're beating you, and use the simulator lots.

If its simply a matter of being outnumbered, then you'll need to expand faster at the beginning.
Emergency building 1-turn colony ships for the first year will really boost you up.

Alternatively, you can build a pile of space stations with shipyards on them, and pump out everything quickly.