I'm sure someone in your class is on benzos... Maybe you can borrow one? Xanax would be nice, I would assume.
Otherwise, some general advice I usually follow, since I get the same wonky thing going on... Avoid caffeine that day, don't smoke (anything), *wink wink*, and try to get a good night's sleep beforehand. And preparation helps, because when you know what you're talking about, it's easier to ad-lib and find the words for things when you're anxious. Practice the presentation a few times with friends, or even by yourself to get used to hearing yourself say the words, get a feel for the flow of the presentation, etc, etc.
It might help to pinpoint why you think you get those feelings--whether it's an insecurity thing, a fear that people are scrutinizing/judging you (intellectually or physically), etc. Then at least you have an idea of steps you can take to get better with it. I was in PA school for a while, and they made us do loads of powerpoints--it got easier for me once I got comfortable with the rest of my classmates, and stopped worrying so much that they were going to think I was an idiot.
I would advise against the alcohol solution, though. You don't want to get involved in using something like that to alleviate the stress/anxiety of professional life, especially so early in your career. You have years to let the HMOs turn you into an alcoholic.
Hope some of that helps.
In any event, good luck on the presentation, and best of luck conquering the public speaking thing. I know where you're coming from.