Proper microphone placement is important for capturing the best possible sound when recording an acoustic guitar. Here are a few techniques you can try:

1. Place a microphone at the sound hole: Placing a microphone at the sound hole of the guitar can capture a warm and full-bodied sound. This technique works well for solo guitar pieces or for recording a full band with the guitar as a featured instrument.

2. Place a microphone above the 12th fret: Placing a microphone above the 12th fret of the guitar can capture a bright and clear sound. This technique works well for recording fingerpicking or for adding clarity to a full band mix.

3. Use a pair of microphones in an XY configuration: Using a pair of microphones in an XY configuration (where the microphones are positioned at a 90-degree angle to each other) can capture a detailed and spacious sound. This technique works well for recording a full band with the guitar as a featured instrument.

4. Use a microphone and a pickup: Combining a microphone with a pickup (such as an undersaddle or soundhole pickup) can allow you to capture a combination of the natural sound of the guitar and the more precise sound of the pickup. This technique is useful for adding flexibility to your recording setup.

Ultimately, the best microphone placement technique will depend on your specific goals and the sound you're trying to achieve. Experiment with different techniques and find what works best for your setup.