In order to make the perfect trailer, you need the perfect clips. After all, the best trailer maker in the world can only work with what they have, and bad quality clips means a bad quality trailer.

YouTube is the best website for this since I'm pretty sure it has every clip in THE WORLD, and you can definitely find something for you.

Make sure the clips match the story, have your cast in them, and try not to confuse the viewer to much. Try to make the clips the same mood as the story, and make sure they are distinguishable (you don't just want a big fuzzy outline for their face).