alright, ill chime in here.....
heres what i do.....and ill post an example of my latest recordings showing the technique....
a single SM57 right up on the grill, pointing straight forward on the middle of the cone (not the dustcap, which is that lil' round thing in the center of the speaker), so this might be off axis as some would call it.
remember, placing a single mic in the very center of the speaker will sound its brightest, placing it at the outter rim will be its darkest..........just stick it in between the 2 spots!
Crank your amp loud (past bedroom levels), if you cant....get an attenuator.
dont suck all the mids out on your amps tone knobs, if you do....you just lost all your tones "body".....
Double track your rhythem guitars so theres 2 guitar tracks per side. So now you have a total of 4 separate guitar tracks.....2 panned on each side of the stereo field (try guitar#1 88% left, guitar #2 75% left, guitar #3 88% right, and guitar#4 75% right).
add VERY minor compression (4:1 ratio and mess with the threshold so its barley working, but helps tame low end rumble on palm mutes and super low flabby notes).
add post EQ (if needed) to fit your mix. My magic EQ frequency is 8k. Keep adding 8k to the guitar tracks untill they sound as bright and shinny as everything else in your mix.
Heres a clip of a song i just finished recording (and playing on) using these simple rules i go by......
http://www.soundclick.com/bands/page_songInfo.cfm?bandID=465137&songID=6813559
again...these are a starting point, or simple testing guidelines.....they my not work for you.....but they work for me.