It really depends on what type of filming you will be doing. I personally like Rode or sennheiser mics but really you get what you pay for. Shotgun mics record more ambient sounds so its hard to control what direction sounds are coming from. Lavalier mics are the ones you would hook up to an actor and only record their voice. It also depends if your camcorder has XLR inputs or not, which I don’t think the hg10 has but I’m not sure. Personally I would buy a voice recorder like the ones reporters use and then using an editing program like final cut or premiere to add in the sounds. Just do some research on different mics and what kind your camcorder can handle. I usually check out http://www.bhphotovideo.com/ for browsing purposes.

I use a shotgun mike, and then mike the actors separately if I want really good sound.

Go to zoom mics recorders. It will blow your mind out!