Working a mic is a bit like using a mixing-board fader to control the level of your guitar, and this can allow you to increase the volume slightly for fills or adjust your overall volume depending on the requirements of the song—getting closer to the mic for a quieter fingerpicking accompaniment part or farther away for a boisterous basher. One disadvantage of only using a mic is that you have to pay close attention to where you’re standing onstage. Wandering too far off-mic will effectively silence your guitar from the audience’s perspective, and veering into the mic accidentally can produce volume spikes and feedback. If you sing and play guitar, you’ll need to pay attention to your proximity to two mics at once.
To get the best results from working a mic, you should become intimately familiar with the mic you’re using. Whether you bring your own or use a house mic, the sound check is your opportunity to check out the characteristics of the mic and determine how to position yourself to get the best volume and tone. Get to the sound check on time (or early), so you can check the guitar first. This gives the engineer time to work on your sound and gives you time to see how the mic reacts.