When you are shooting on the go and alone, the easiest way to get good audio of your talent is by having them wear a wireless lavalier (clip-on) microphone. The basic steps of this are simple: plug a lavalier mic into a mini voice recorder, put the lav on the talent and

If you want quality lav mic audio, the cheapest, easiest, and most worry-free solution is to plug a decent quality lav microphone into a portable recorder and have your talent wear the recorder.  You then sync it in post with Pluraleyes or FCP X’s synchronize function.   I have found this system reliable enough