hope this article helps
Good condenser microphones for acoustic guitar recording include the Oktava MC012 ($99), Groove Tubes GT55 ($250), or the RODE NT1 ($199). The reason you want a condenser microphone rather than a dynamic microphone is very simple; condenser microphones have much better high frequency reproduction and much better transient response, which you need for acoustic instruments. Dynamic microphones, like the SM57, are great for electric guitar amplifiers which don't need as much transient detail.
Microphone Placement
Take a listen to your acoustic guitar. You'll find that the most low-end build-up is near the sound hole itself; the higher-end buildup will be somewhere around the 12th fret. So let's look at the two types of microphone placement I mentioned earlier.
Single Microphone Technique
If using just a single microphone, you'll want to start by placing the microphone at about the 12th fret, about 5 inches back. If that doesn't give you the sound you want, move the mic around; after you record it, you might want to give it extra body by "doubling" the track - recording the same thing again, and hard-panning both left and right.
Two-Microphone (Stereo) Techniques
If you have two microphones at your disposal, put one around the 12th fret, and another around the bridge. Hard pan them left and right in your recording software, and record. You should discover that it's got a much more natural and open tone; this is really easy to explain: you have two ears, so when recording with two microphones, it sounds more natural to our brain. You can also try an X/Y configuration at around the 12th fret: place the microphones so that their capsules are on top of each other at a 90 degree angle, facing the guitar. Pan left/right, and you'll find that this gives you a more natural stereo image sometimes.