Depending on the equipment you chose, setting up your sound should be relatively straightforward. If you have a lav mic, have the subject pass the cable up through their clothing, and make sure the mic itself is clipped on the chest in a way that it is not obtrusive and won't rub on clothing. Make sure that you have live batteries installed (and bring spares). If you are using a shotgun mic, get it as close to your subject as possible, while keeping it out of the frame.

You'll want to make sure that you have the input levels on your camera and/or mic set so that clipping does not occur (this happens if the sensitivity is too high and loud sounds get "clipped"). Use headphones to monitor this if possible.