I have always been a big fan of video, and especially video quality. About a year ago I went out and bought a blue yeti to help me with my video production. Something I have always said is that Audio is more important than video. I promise that your audience would prefer bad looking video with good audio rather than bad audio with good looking video. With that in mind I currently use my GF2 to record video and then use the Blue Yeti to handle all audio I need. Really you can do this with any camera or microphone, so here is how to sync a camera with an external microphone.
Really when it comes down to it, you only need two real steps to follow. First is while both the camera and microphone are recording clap 3 times, with a second between each clap. That will give you a reference point to sync the clips on when you come to edit your video later. Then all you need to do is import your footage and audio into your video editor of choice. I use (and recommend) Movie Studio 12, but you can use any editor that supports multiple tracks. One imported use the clap reference points to line up the audio from the microphone with the audio from the camera, the video above shows how to do that easily.
Of course then you can remove the audio from the camera and group the external microphone audio with your video, then your done! If you found this helpful be sure to join the Mailing list and Subscribe to me on YouTube.