There are several ways up the mountain when miking an acoustic guitar in the recording studio. One of my all time favorites is using a clip-on lavalier mic! I find it to be the warmest and most detailed sound, but it also serves to solve another huge issue we have in the studio: too much moving around!
As you know when the actor/singer/player moves “off the mic” there can be a drastic change in sound quality. This is particularly an issue when recording acoustic guitar. But using a lav mic which is physically clipped onto the guitar’s sound-hole solves this problem. It also gives the player much more freedom to express themselves!
Another technique I like in tandem with the lav mic is to use a shotgun mic aimed at about the 12th fret. NOT directly at the sound hole. You can actually mix-and-match between both of these microphones for the perfect sound (but be careful with your phase. Try nudging one of the mic tracks by a few samples to line-up again in your Digital Audio Workstation (Pro Tools, Cubase etc).
Like all things in the studio: there are no hard rules. The best rule is whatever makes it sound amazing! Have fun, experiment and let us know what works best 😀