I did Public Forum in high school for four years. The main thing I like to see in a debate is logic. I don't necessarily care if you're completely dominating the flow; if you're making logical arguments and clashing with your opponent, you have a good chance to win my vote.
I'm okay with some speed, but don't go overkill. If you speak too fast to the point where I can't understand you whatsoever, you're going to lose points.