attempting to address the original question now...

I'm a guitar player, so my approach to mixing guitars (even tracking them for that matter) is going to be different from folks for whom this wonderful instrument is not their priority<G>...

I'm reasonably certain I have no recipe, or even favorite tricks, I doubt that I've taken the same approach to mixing a song more than a couple of times over the years. One habit I developed back in the days when 8 tracks was a luxury was committing effects, and even processing for all my tracks. Part of the beauty of committing to effects and processing is that it leaves you fewer decisions to make at mix-down time!

I like to put rhythm guitar tracks off center. Sometimes I'll be symmetrical about it, but not often. I like some modulation on most if not all guitar parts - phasing, flanging, chorus, a rotating speaker, whatever, just something to animate things a bit. Now that I can (computers can be handy) I like to synchronize modulation effects on different instruments. I di wish there was a better way to do multiple time bases from a single clock... that sounds awesome, but it isn't a trivial task in hardware or software!

I suppose I'm a bit of a sheep when it comes to lead vocals, lead guitars or whatever instrument is being highlighted... I'll put them front and center. It's a convention if nothing else.

Bass guitar is probably the most challenging instrument to fit into a mix... it sort of wants the same bit of bandwidth as some of the drums, and you do need to help it out. My first attempt is always to find a bass sound (either from a soft synth or by choosing the right player/instrument/amplifier/microphone) so that it just fits. Many will agree that's easier said than done!

So then I try different tricks, and this is just the opposite from guitar for me, I do use my same tired old tricks<G>...
- EQ first, cut only, try to find complimentary center frequencies for bass and kick
- Compression with a side-chain input next, use one to control the other, which is which depends on the song
- apply reverb to one but not the other, again choice depends on the song
- move the bass just off center, I'm always wary about moving the kick off center, though I've heard it done well, I just muck it up
- believe it or not, every once in a while delaying the kick can really add some punch, delaying the bass has never worked for me
- sometimes I'll add a sound effect, bricks, pots and pans, something purely synthetic, to accent the beginning of the beat.

That's about all I can think of at the moment...

Rhythm Electric Guitar: Double track with separate takes, pan as desired, eq out high end to create the impression that the guitars are a little set back from the listener and lead instrument/vocal, apply reverb to create a sense of depth, not reverb for effect. The tails here should not be audible or just barely when track is soloed. Reverb used just to create a space around the guitars. This places the rhythm guitars a little back in the mix. Gives that far away impression and adds depth to the mix.

I know that clipping is bad, I just picked up in one of the forums a while back that when recording digitally you never want to exceed -12db.

Unfortunately in digital recording systems converters are not all calibrated the same. The thing to be mindful of is the signal you are sending to the converter from the outside world/analog gear, and that signal should be +4dBvu which will correspond to -18dbfs on most professional converters and perhaps -14 dbfs and less on others. If your converter is calibrated to -18 dbfs, then inside your DAW that is the ideal RMS level for recording. Your transients will be higher. Getting a good plugin level meter that detects peak and RMS levels is helpful. The point here is that if you are exceeding the RMS level that your converter is calibrated to, then you are sending in a signal that is too hot.

I like the SI plug as well - great, usable sounds that don't need much to sit properly in the mix.

However, I only ever use Midi bass as a sort of placeholder with the intention of learning it for real and recording it myself later.

There's also some good ones in Dim Pro - electric, acoustic, upright etc