Paying close attention to the previous advice on organization will help with some of the basic issues of delivery. Assuming you have good notes to ground you, you should think of the following:
Slow down and speak clearly! Your voice probably has to fill a rather large classroom space. It has to compete with its own echo. Your words have to sink into your classmates brains (it could be a long way down!), and your classmates may be taking notes or studying your visual aids while you speak. Speak more slowly and enunciate more clearly than you think is proper.
Try to keep your delivery flowing evenly, with as few awkward pauses and fillers ("ah...," "er...," "like," "you know,") as possible. Of course, we usually add these filler words unconsciously, so it takes practice to root them out.
You will usually give a more forceful presentation if you stand rather than sit. You are freer then to use body language to help get your ideas across. A podium or reasonable facsimile will help.
Can you think of a way to involve your classmates as participants in the class, not merely as auditors? They will be much more favourable to your presentation if you engage their help. Ask questions that elicit opinions rather than facts (and don't be put off by a few seconds of silence in response).