It's not a good idea to mix any lead instruments in with other instruments to a subgroup. Keep your lead guitar separate, as well as any other leads. If you have electric rhythm guitar and acoustic rhythm, you should keep these separate also. It helps to be able to retain control of the individual characteristics such as EQ and effects. You will want to EQ instruments that share the same basic frequency range in a way that allows each to be heard distinctly. This is called "complimentary EQ". Boost one instrument at the desired frequency, and cut the other at the same freq. Even just a couple of dB with a relatively narrow bandwidth can make a big difference in the clarity and "fit" of your mix.

I also would never submix a lead vocal with backing vox, for essentially the same reasons. You lose control over the individual characteristics.

As far as drums go, I like to keep my snare, kick, toms, and overheads on separate tracks. Sometimes, I will submix the toms and overheads, but I never lose the individual snare and kick tracks.

Now there are some exceptions to everything I just said. I will almost always record a mixdown of the instrumental only to two tracks, and a vocals only mix also. This gives the customer (or me) a performance backing track to use for live performance without a band. The vocal mix just makes it easier to go back in a hurry to try a different mix out with the vocal levels up or down a few dB.

As far as compression goes, I almost always do initial tracking with an appropriate amount of compression to keep things smooth and get a "hotter" track. Then backing vocal subgroups are compressed as a group to make them sit well in the mix, and provide a smooth cohesiveness. It keeps the individual tracks from standing out, and makes them work better as a whole.

Depending on the song and the sound I'm looking for, I will apply some light compression to the stereo mix.

Thanx! that's exactly the kinda stuff i'm looking for. 8-)