tree thing sounds good, maybe tape it to your helmet for a little, or even the quad, have someone ride next to you, someone lay on the floor. just be creative with what you have.
Edited:
some other good 1 time shots is lay the camera on the floor, and have the quad run over it centered (good for an opener/closer), have a few fly bys (keep camera still, and person goes by fast on quad), have camera person stand in woods (so it looks like an animals veiw of whats happening) They might sound dumb, but it looks really good if done right.
And when/if you tape the camera to something, depending on the quality of the camera, it may glitch when big/small bumps are hit(all depending on the camera!). So just try going to the helmet first, and see how that works out.
I'll let you know if I think of any more.