I've found that i don't use alot of mastering effects, I've tried it both ways, of course it depends on the song or track, but if each track is eq'd well and the right effects etc. are used on each vocal/instrument, that makes the mastering much easier. Also, like Stainless, I'll master and listen to it, then if something needs fixed, I'll re-master it.
As said in other threads here, get great tracks to begin with, that makes a world of difference on the rest of the project.