I recommend Scott Hanselman's post (previously mentioned). I've written up a post with some tips, mostly for selfish reasons - I review it every time before I give a technical presentation:
Tips for a Technical Presentation
If you're using a console prompt, make sure the font is readable and that your paths are preset when possible.
Take 15 minutes to install and learn to use ZoomIt, so your audience can clearly see what you're showing off. If you have to ask if they can see something, you've already failed.
Probably most important is to have separate Visual Studio settings pre-configured with big, readable fonts.
