I typically put an sm57 up close to the guitar, somewhere between the sound hole and the 12th fret (depending on how much bass I want in the mix) and my at3035 cardioid LDC a few feet away, just above the players head, angled down towards the guitar. I really like micing this way because the two mics complement each other (one gets mostly bass and low mids, the other gets mostly highs and high mids) and the strumming noise comes through very distinctly, which I like hearing in the mix.

When I have enough extra cash lying around, I plan to grab another 57 for various uses, but one will likely be moving to basically what avinashv said, using the 57s in a stereo configuration, and the ldc as a third room mic. Just make sure your in a somewhat small carpeted room, preferably with something up on the walls (for sound diffusion) before you use a room mic.