The best way to rehearse your presentation is in front of people. Any people. Half of the reason we’re all so anxious about speaking in public is — the public. We worry about how our comments will be received, and if we look goofy saying them. So, while rehearsing in front of a mirror can help a bit, the best practice is in front of real people; colleagues, spouses, children, strangers on the subway.
This will help you enormously and you’ll quickly see just by their expressions what works and what doesn’t work. You’ll feel more confident.