I'll probably repeat much of AKinDC but there's some good advise there so here you go:
1.Tripod...bring it and use it! A tripod not only lets you get steady well framed shots, it lets you step a little away from the camera so even if you're by yourself the interview subjects are looking off camera and not right into the lens. With a tripod you can also get a variety of focal lengths. (wide, med, tight and extra tight) I noticed all of your shots here are the same focal length (with the zoom all the way out and the camera about 3-5 feet from the subject/object)
2. Start with great, compelling video or sound. Grab the viewers attention right off the bat. I try to start with nat sound or a sequence that brings the viewer into the location of the story I am telling. If it is really compelling or emotional I'll start with a soundbite but this is pretty rare. This type of story is perfect for using sound to set the scene with a ton of opportunities...swishing water, rocks, laughter, comments, or whatever else you hear out there.
3.I liked the music, you may want to ride the levels so it is down during interviews and nat sound
4.Don't have people hold their own mics for interviews, put a lav mic on them or hold it yourself. If you have no other option, have them hold it but frame it out of the shot. (it will still look awkward though)
5.Especially for feature work like this, I try to talk with people while they are doing whatever we are talking about. Maybe put a lav mic on him and have him talk about panning while he is doing it. You also could shoot the interview tight for a few questions, then wide for a bit and mix up your shots. (variety is important to keep things interesting)
6. Shoot in sequences. Wide, med, tight, extra tight. Since panning for gold is a repetitive action it is really easy to get a 10 second wide shot of panning, then move to get medium shots of the action, then tight shots of a pan, hands, eyes etc... Remember to make your wide shots really wide and your tight shots really tight, it makes the edit so much easier and the story more interesting.
7. I liked how you used some nat sound breaks of the panning
8.Great close up perspective showing the gold nuggets!
Hope some of this helps...