Like most developers, I don't get a lot of experience giving presentations. The golden rule is: practice, practice, and more practice. Then incorporate the feedback from those practice sessions into your presentation. Of course, it helps to perform practice sessions in front of people who have seen a lot of presentations, as we did yesterday with Connie Marthinsen and Rob Zelt in preparation for the Raleigh Code Camp.
There are also a number of pages with excellent advice to would-be technical presenters, starting with Scott Hanselman's Tips for a Successful MSFT Presentation. Scott includes essential advice on text legibility:
Lucida Console, 14 to 18pt, Bold. Consider this my gift to you. This is the most readable, mono-spaced font out there. Courier of any flavor or Arial (or any other proportionally spaced font) is NOT appropriate for code demonstrations, period, full stop. Prepare your machine AHEAD OF TIME. Nothing disrespects an audience like making them wait while you ask "Can you see this 8 point font? No? Oh, let me change it while you wait." Setup every program you could possibly use, including all Command Prompt shortcuts, before you begin your presentation. That includes VS.NET, Notepad, XMLSpy, and any others, including any small utilities.
I've found that the most readable setup for Command Prompts is a Black Background and with the Foreground Text set to Kermit Green (ala "Green Screen." Yes, I was suspicious and disbelieving also, but believe it or not, it really works.) I set Command Prompts to Lucida Console, 14 to 18pt, Bold as well, with much success.
You can set many of the "un-set-able" font sizes in VS.NET, including all dialogs and menus, by launching it from the Start|Run menu like "devenv.exe /fs 14." It will stay this way until you set it back with "devenv.exe /fs 8". Also, set the font size to LARGEST in Internet Explorer and remember that there are accessibility features in IE that allow you to include your own Large Font CSS file for those web pages that force a small font via CSS.a
For simplicities sake, I like to keep a separate user around call "BigFonty" (choose your own name). He's an Administrator on the local machine and he exists ONLY for the purposes of demonstrations. All the fonts are large for all programs, large icons, great colors, etc. It's the easiest way to set all these settings once and always have them easily available.
Scott also recommends Venkatarangan's page of presentation tips, which is high praise indeed.
Brad Abrams, Eric Gunnerson, Robert Scoble, and Don Box (quoted) also have good, brief tips for PDC-style technical presentations. For a completely non-Microsoft opinion, I found Conference Presentation Judo helpful-- but beware the three hour format caveat.
The art of giving an effective presentation is, of course, a bajillion dollar business outside the insular world of software development. So there is no shortage of books, speakers, and websites offering their take on this. The ones I see recommended the most are Presenting to Win (by John Lam) and Beyond Bullets. Beyond Bullets is mostly about PowerPoint abuse-- as aptly demonstrated in this PowerPoint presentation of the Gettysburg Address.
While these links are all undeniably helpful, remember: reading about being a better presenter will not make you a better presenter! Read about it, and then practice in front of an audience.