Cant say for individual biomes, but something flat-ish is a good idea unless you like digging. Snow biomes will mean ugly defrosted patches if you're careless with torches
Depends on your style-
I always go next to an ocean biome- looking for a steep dropoff into deep water.
-Mostly because underwater builds look cool, but for normal people your quarries will hit the good stuff quicker and it kind of hides the holes.
Nearby building supplies are a must (I love basalt and marble)
Normally I like a decent view- so nearby mountains/tall forests are a must.
This usually means walking several km in game (SMP) and burning through many seeds or using mystcraft (SSP)
Don't pick an area based on finite resources (oil spouts)- when they run out you're left with a crappy area and no oil (and often a ruined ocean).