This is my strategy:
1) At the very start of the game, set tax rat to 40%, this puts your economy in the green at the very start, while keeping your morale at a decent level, I also buy an entertainment network as an added precaution, it's cheap too.
2) Constantly check your production bar, if you're ahead of the game, set it to zero so you get a couple 100 credits per turn for a max of 10 turns, this especially works if you're Terran or another race with strong diplomacy, then you can more easily get the techs you didn't research for those turns.
3) Keep military at a manageable size, too small, you won't live long enough to have an economy, too large, and your economy crashes.
4) DO NOT RUSH BUY EVERTHING! I CANNOT EMPHASIZE THIS ENOUGH!
5) Only rush buy a few colony ships to get your empire running, then, on each planet, rush buy one factory so as to pump up your production, then get some econ. buildings going.
I follow this strategy, and it works pretty well, if it doesn't work for you, then tweak it a little bit.