Here are some tips I've picked up through various self-help books/articles/TED Talks on the subject (because I was always a terrible presenter) and these are what made the biggest differences for me:
Prepare excessively. Know your presentation backwards and forwards, record yourself practicing for review, and ask others for feedback (preferably friends you trust to give you honest criticism!)
If you can, scope out the venue/room beforehand so you can at least mentally picture yourself presenting there (and doing a kick-ass job).
Before the presentation, hype yourself up by taking some "power poses" and listening to your favorite power playlist (whatever songs make you feel good). Obviously you will want to have gotten a good night's rest and have selected ahead of time an outfit for the presentation that makes you feel like a boss.
During the presentation, maintain good posture, try to let your arms/hands express yourself naturally as you speak, and maintain eye contact with the audience when possible (starting from one side of the audience and holding your gaze for 5-6 seconds before continuing a "sweep" through the audience works best for me in terms of gaze). If you make a small mistake, don't fret! Simply move on and the audience will, too.
Well, those were my best tips for how I improved my own public speaking-skills. Hope that helps!