4.1 Mixing:
When it's time to start building your mix from the tracks you've recorded, start with the bass drum, then mix in the bass guitar. Try not to boost the low end to try to make it solid. All you'll usually get is mud. If you want the bass drum way up front, boost the higher pitches of the kick and use the bass guitar for the deep lows. Use some compression. It's really helpful to A/B your track to a commercial CD to get a feel for the sound. The kick is especially good to listen to. Although it really drives the song, it still usually sits in the mix very well. Check the low end in the car and on your home stereo. Is the low end muddy at all? Even at (reasonably) high volumes or with the bass knob boosted, it should remain fairly clear. If not, consider a multi-band compressor rather than EQ.
Now add vocals (see vocal recording section)... then the rest of the instruments in an order you feel is important. Always keep in mind that vocals are the main part of the song, and they should be very clear. Mixing them in early helps, so you can blend other instruments around the vocals, rather than the other way around.
To thicken up tracks that just don't seem as full as the others, try using a wide panned delay between 5 and 15 milliseconds. Pan the dry signal to one side and the delayed signal to the other side, and try to keep the levels pretty even. I use this on some bass and keyboards parts, because it helps to hide my lack of real talent on each instrument, plus adds a good deal of depth to a flat sounding track. I usually use both low and high pass filters to catch only the midrange...from about 300Hz to 3kHz or 5kHz. Adding the delay to the original track in mono is also effective sometimes, as it just thickens a bit. This works better with shorter delay times (around 5 ms). Be forewarned: When messing with delays like this, it's VERY easy to make a song that's not mono-compatible. You should sum the dry and wet tracks in mono, to be sure there is no strange comb filtering effects.
All of your preliminary mixing should be done with no reverb. Mix it dry, and add a splash to thicken and liven it up. Becareful not to over-do it (unless that's an effect you desire).
Also, if it's not a terribly complicated mix, you might try printing a couple versions of it. Most commonly, I run off one version that I think sounds right, one with a bit less vocal, and one with a bit more. This allows you to sit back and listen to it later and determine which way it sounds best. I like to wait a few days so it sounds "fresh" again. If you're recording for bands other than your own, they'll feel more satisfied with the end result if they can choose the final mix.
4.2 Special Considerations for Mixing
and Preparing for Mastering:
There are a few objectives to consider when mixing a song in preparation for mastering. You want a well balanced good performance. EQ and compression should be used minimally. Just smooth out the tracks that need it, but be subtle. You shouldn't use a limiter, or compress the whole mix. Try to get rid of silibance before mixing with pop filters, changing mics, positions, etc, or with a de-esser (or compressor w/ sidechain + EQ). A little bass roll-off on the vocals allow it to sit better with the bass. Also avoid aural exciters. They're fine for playback or revitalizing an old tape, but not for a pre-mastering step. When panning the instruments in the mix, keep your vocals bass guitar, bass drum, and snare in or near the center. The rest of the instruments should be sonically balanced around the center. Make sure you pay particular attention to the higher frequencies in the mix. It's pretty noticeable if they're off balance. For a good example, a bright clean guitar sits well opposite the hi-hat. Listen to how the bass guitar and drum fit together. Don't over do it. Most home studios will probably be sending DAT tapes for mastering. It's a very common format, and the hardware is very reliable. Call the mastering engineer, and ask him/her what levels they prefer. Some like the levels a little low (peaks at -3 dB). Remember that digital signals clip horribly and should never be allowed to exceed 0 dB. Even minor clips will make the signal sound grainy. If you're sending your mix on analog tape, it's possible to run it a little hot, although you should still ask the engineer. Peaking at +3 dB can add just a little color.