DO read Kathy Sierra's advice on presentations (eg. this)
DO Work out what you're trying to achieve and what you're trying to get across to your audience. And in working that out, make sure that it's at a level suitable for the audience. Too far in either direction is bad.
DO Think before launching into Powerpoint. Do you really need it? Depending on your material your presentation can be much more dynamic and engaging with a big pad full of butchers paper.
DO If you do go down the butchers paper route, make sure that you prepare your "pages" first. Do all of your drawings and writing in pencil on your paper before the presentation. During the presentation do all of your drawing afresh in texta. You can also leave yourself notes or prompts - the rest of the audience won't see them, and it won't spoil the feeling of sponteneity.
DO Do some (if not all) of your drawings during the presentation. Static drawings (as are so often used in Powerpoint presentations) lose the dimension of time - it is much easier to disseminate information about the progression of ideas if you're able to lead the audience without overwhelming them with fancy glitz and flashing things.
DON'T (as a rule) use lists of bullet points. Often people will present a list of bullet points, and start reading through them. The problem is that the audience is usually distracted by reading the points (since you gave them all at once) and won't listen to you while they're doing it.
DO Practice - good presenters (eg. Steve Jobs) claim to use a 10:1 ratio between preparation and the presentation itself.
And, on the subject of Steve Jobs - DO check out this, for a good analysis of slide styles.
(addendum): A short time after this question was posted someone gave me this link to tips on presenting to small audiences.