Drew posted this awhile back, and it's time for a repost:
http://www.badmuckingfastard.com/sound/slipperman.html
Read that. It's great. Long read, but very educational.
Here's my take:
Recording rhythm guitar is one of the hardest things to do well. You have to have a great signal chain, you have to have clean/clear mics, good d/a converters & mic preamps, the right sound on the amp, and the right mic location on the speaker.
Most important is the right sound on the amp and the right mic location on the speaker. You can get by without some of the other things. I've found that my recording sounds are very different from my live guitar sound. My recording sounds don't sound incredibly impressive when played with my band live, but they are great when put to tape. Speaking from personal experience, your live sound almost never works in a studio.
Your mic picks up sound differently than your ears do. That's why it's practically mandatory to have a quality set of headphones. Put the headphones on, strap on your guitar, then play and start messing with the mic position. It can take hours to find the sweet spot (or in my case, years!), but once you do, you'll know because it'll sound completely different than the other parts of the speaker. Once you have that spot located, start messing with the amp's dials and see what sounds you can get from it. That's the process most engineers use (or they use a variation of it, i.e. having a tech move the mic
).
Your recording sound should have more mids, tons more presence, and a lot less bass than your live sound you're used to out of your amp. The mids and presence are magical when recording. A lot of guys (myself included) use an extra EQ after the preamp stage of their rig/amp for additional boosting/cutting of those frequencies. Your bassist will more than make up for the lost bass in your sound. Also, if you haven't already, lower your gain at least 2-3 clicks from your live sound. Your sound will be heavy enough with the gain on 6, and it'll sound mushy as heck on 8 or 9.
A quality condenser mic will pick up a great sound for you. For punch, clarity, and the sparkling high end that you hear on pro metal albums, you've gotta have an SM57 or Beta 57, IMO. They add something that you don't realize until you use them. They also
do not sound very good unless put in the perfect spot, which is why a lot of guys buy them, try them, and are disapointed by them. I didn't like mine at first either until I learned how to use it. Once you find the sweet spot on the speaker and put the 57 in that spot, your sound will be golden.