Ideally you will have an external microphone and be able to freely move the camera around without having to be concerned about how your shot will affect your audio.  However, you may find yourself in a situation where you are working with the microphone that is built into the camera.  Although this is the second worst-case scenario (the worst case being no microphone at all), there are a few things that can be done to get a better sound recording.  If possible, get right up next to the sound source (whoever is speaking or what music is playing for example) and stay there.    Always wear headphones plugged into the camera so that you can monitor what you are recording and (if you can) experiment with finding a location that sounds best before settling in.  Avoid moving around a lot and DO NOT touch the microphone (be especially careful when adjusting the zoom or focus).  There are a few tricks that can be done in post production to fix mistakes, but remember – nothing is going to make awful tracks sound good.