Q: Can you tell me the best way to record acoustic guitars in the studio and also on stage?
Three top tips for the studio...
One - Get a really good guitar. Don't just judge by the brand but go to as many guitar shops as you can and try out everything in the most expensive price range you can afford. Take a portable recorder with you and consider what the instruments sound like when recorded, as well as how they sound to the ear.
Two - Record the guitar in stereo. The simplest way is with a coincident crossed pair of microphones. A stereo recording usually sounds much better than mono. Bear in mind that if you separate the mics spatially, you are making the job more difficult. That would be a challenge at a higher level.
Three - Aim the microphones at the 'golden zone'. It's always good to experiment, but frequently the golden zone for acoustic guitar is halfway between the edge of the sound hole and the point where the fingerboard joins the body. This is generally a good starting point.
Now, top tips for the stage...
One - Get a really good guitar...
Two - Be realistic about your expectations. Since the guitar will be competing with other instruments on stage, your choice of microphone positioning will be limited. You will have to position the microphone very close up so that other instruments won't intrude into the guitar track too much. This unfortunately will degrade the sound quality that is achievable. A miniature microphone taped close to the sound hole is a common solution.
Three - Be very wary about using the internal pickup. Many internal pickups sound dreadful. Make a test recording first and see if you can live with the sound quality that's coming out of the jack socket.
It is always good to bear in mind that the more instruments there are on the recording, the less the sound of the acoustic guitar is likely to matter. But if the acoustic guitar is exposed, then you really will have to take as much care as you can.