Thank you guys sooooo much! I'm surprised by how much helpful feedback I recieved in such a short time. Now to answer some questions of my own:
Marecare: Honestly I really don't know much about the history of this horse or other things like how much turn out or riding time he gets. He's a lesson horse and I'm only there twice a week. I'm going to the barn in a few days though and I'll try and get some more info for you.
Also, I don't think he's in pain or anything from something recent like a saddle. He's been biting for quite some time now. I have a feeling that it's most likely because all the young clients that rode him in the past maybe were to quick in tightening his girth or whatnot...
I have to say, your 3 second rule sounds the most effective. I think I'll try it. As for the nose smacking thing, even if it did work, I don't think I could bring myself to do it, I love him too much.
So, do you all think that if I apply these tricks on him he eventually won't continue to bite me or do you think that there are just too many people riding him? Well, anyways I'm definitely going to try these tricks.