A simple technique for a good sounding recording is to start with a single condenser mic about 12 inches in front of the guitar pointing at the edge of the hole and fretboard. Be careful of too much low-midrange as you get close to the sound hole. If you want stereo, use one mic pointing at the hole, and another pointing at the middle of the fretboard.
In addition to using mics in front of the guitar, a mic or 2 can be placed near the players head, pointing down at the guitar. Experiment with placement and always use your ears as a guide. Try recording each mic onto a separate track and then soloing each one to decide what you like or don't like about the sound.
Now that you've got all your tracks recorded, you've got a few options. One is to mix all the mics and process the tracks gently to produce a clean, single guitar track. Another option is to process each mic completely different from the others and use effects to produce some new and wild textures.
Starting with the stereo mics in front, pan one hard left and the other hard right. If your mic placement and room are good, this usually produces a clean stereo image. However, if the recording room is not the greatest, try panning them 50-70% to each side instead of 100%.
With the over-the-shoulder mics, solo each track, and if you find a frequency that you like, boost it a bit. If there is a problem frequency, cut it a little. This way you can get the best of each mic and mix them to make the best sound.
For that 'army-of-guitars' type of sound, try using some effects such as delay, drastic EQ, and distortion on a few of the tracks. Pan some hard left and hard right. Leave at least one track dry and unaffected to give some solidity and ground to the sound. Another way to get a thick sound is to double or triple track the same guitar part. Each performance will be slightly different and provide a great cohesive sound when mixed together.
