I tend to try blending different mics. I'll put a 57 close and adjust it until it gives me the sound I want, then I'll put a C414 in a figure-8 pattern several feet away. Sometimes I'll pick one track out of the two resulting, but usually I'll pan them differently and blend the two to get a nice, full sound.
But it just depends on what I'm recording, really. The type of sound I'm trying to capture, etc. If you have a great guitar sound in the room, it's a lot easier to get a great guitar sound on the recording.
Don't be afraid to experiment, either. I've gotten good sounds by putting a small-diaphragm condensor in the back of an open-back guitar cab and reversing the polarity on the mic, then mixing it with a large-diaphragm condensor in front of the cab where it will capture more room sound. Sometimes an SM-57 a couple of inches away gives me the sound I want with nothing else added.
Also, remember that what sounds good by itself isn't necessarily what will sound good in the mix. If you have enough tracks to play with, don't be afraid to lay down a lot of tracks with different mics, preamps, etc (make sure you keep notes on which track used which mic and pre, how they were set, and so forth for future reference) and then listen to different tracks in the mix later with drums, bass, vocals, and whatever other instruments you're recording. Sometimes a track that sounds full and rich by itself just sounds bottom-heavy and muffled in the mix, while a track that might sound thinner alone might cut through the mix and give you a clearer sound.
And that's my completely amateur and not-guaranteed-to-be-accurate take on the matter. Of course, I've been wrong before...