i've been having good luck with the following method, up to (and including) painful difficulty:
set taxes to 49% and spending to 100%; pop growth is managable, econ is healthy
set military/social/tech spending to 26/25/49
research the techs that give empire-wide production/morale/econ bonuses first; large+ galaxies, get sensors and build 1 or 2 more (custom) survey ships to find those big planets, resources, and 2500bc anomolies.
design a new colony ship with speed 3 ASAP; every time you get a new engine or miniturization tech, see if you can build a faster ship
start all new colonies factory > factory > starport, and buy the first factory; when your starport comes online, you'll be automatically taken to the planet to plan out production again. also, two factories are a healthy base for upgrading tiles in the future.
i never research weapons or defenses until war has been declared upon me. the only exception is the branch with +soldiering; i get all of those as soon as they are 4-5 week time investments.
i hope i didn't give too much away

building well-balanced, profitable planets is a viable strategy at the lower difficulty levels.
figuring all that out and developing my own strategy was most of the fun. i'm now working the kinks out of bumbleputz's planet specialization theory. it's pretty crazy... 4 mfg starbases pumping up 4 production/tech planets and i can't get the other 12 or so $$$ planets to turn a profit at 69% taxes and 75% spending >.< time to demolish some factories i think...