As always, Tarekith's stuff is worth a read.
I'm also in the process of finishing up an album at present and working through getting everything just so, including the levels.
I've done pretty much all of it within the mix itself, tweaking the levels and ensuring there's no clipping above 0db. I've used the odd compressor here and there, though only gently, just to lift parts like soft piano playing and the like to fit in nicely.
However, I've set-up a version of the Analogue Warmth mastering string in the master channel of each track which uses some very mild saturation, gentle compressor and a tiny amount of EQ (only varying by a max of 2db +/- finished off with a limiter. I keep the saturation and EQ the same on all tracks, just to give them a touch of 'signature sound' and then vary the compressor threshold and ratio so I get the odd peak at around 2db, and then use the limiter set at -0.2db with the attack and release reasonably high as my stuff is more downtempo and evolving. That's the technical side of it.
I then listen to the tracks on the PC, stereo and iPod, either with speakers or headphones, to hear how it sounds in various environments, if any little tweaks are needed then I can do them back in the mix leaving the master string alone. The end result is hopefully something that sounds good, clean, even, and recognisably mine
To sum up, the basics are EQ, compression and limiting. Don't be afraid to use the spectrum analyser aswell, might hint at points where you need to tweak the EQ.
