three ways to record an acoustic guitar.
Use the X/Y arrangement stereo micing technique. Use two exact models of SD. Start with both mics at a distance around 5-7 inches or so. Adjust the distance of both mics accordingly based on playing style. If you are doing primarily finger picking, you can get in tighter, if you are strumming, back it off a bit. The tighter in you go, the more detailed of a sound you will have… the farther out you go the more “body” you will pick up. Also experiment with the horizontal placement of the mics on the guitar.
The X/Y is my go to method. You have a lot of flexibilty come the mixing stage.
Another one i have used to good effect is the spaced pair. Also referred to as the A/B pair, this technique employs one SD pointed at or around the 12th fret, and another pointed at the bridge. You have to employ the 3:1 rule else you will create phase issues. Basically if the mic pointing at the sound hole is 7 inches from the source. Your second mic has to be three times the distance of the first mix.
This method was what i used before i got stereo mics as only had two different mics.
Last method is the over the shoulder.
This is a variation of the spaced pair (A/B technique), with one mic placed aiming at the guitar towards the bridge (or 12th fret) and another aimed down at the body from over the performers right shoulder (assuming the player is right handed). The tight mic captures the presence of the instrument, while the shoulder mic emulates the perspective of what you would hear if you were playing the guitar. Work with varying distances, placements and angles with the shoulder mic to find the sweet spot. Again the 3:1 has to be employed else phasing issues arise. I have tried this method just once and found it a pain. If the guitarist moves too much it can effect the sound too much. And if the player goes to the toilet etc very difficult to get them back in the same place!
With recording acoustic guitar its all about finding the sweetspot but never underestimating how bad phase can be if you get in proper placement.
EQ. You can put on a high pass filter up to about 250hz. I tend to put a little in the 1-4 k range to add some sparkle. But general rule is removing frequencies to help sit it in the mix.
Effects. An acoustic guitar has no effects as an instrument so you wouldn't want to add IMO. other than some room reverb. But thats only if you didn't capture any on the original recroding. My booths are setup flat so i generally add a post bus of room verb after the EQ. Just a tad though. easy to put to much on.
Recording acoustic guitar is trial an error in regards to placement, just keep moving the mics around until you find the sweetspot but always stick to the 3:1 when using two mics (doesn't apply when using stereo placement)
Hope that helps.
Tim