If you have the time, bring headphones, and go record something you don't care about.
Talk into the mics as you set levels. Call out your level changes, then go listen back. If it's convenient, go outside and listen, or wait for set break and do more experimenting.
If you don't have time to get to a real venue and try it with a band or DJ, you can use your home stereo, set to moderately loud volume. Try to simulate what you expect to hear from your location at the show you want to record.
Have fun!