if the owner allows it, I play some racks with other people who are waiting around, or a buddy. I'd pay to rent a table if I had to, and I know it'll be a long wait. Also practice lagging a minute or two before you expect the final rack to end. Having just 5 or 10 practice lags vs another guy's 0 pretty much ensures you'll win it, and winning that first break in a tournament might be a big difference.
I think you've just got to turn it back on after a long wait and don't let the wait influence your play. Don't feel like you have to be shooting pool every minute between matches to stay warm. Don't rush when you finally get down to it. You might take care of anything that might be making you even a little uncomfortable... eat if you need to, close your eyes a minute or two, stretch, get a backrub*... hell, even change your shirt if there's something about it that's bugging you. Get rid of all possible small distractions.
*or some pleasant alternative. If you want to shark your next opponent and get a sure win, just ask him to administer it.
