Practicing your talk

Practice talk in as close to live conditions as possible. Every variable that is different between your practicing and actual talk presents risk.

One thing many speakers forget is that the resolution on their screen will be much lower than usual when plugged into a projector. It's an extremely good idea to drop your resolution to around 800x600 and run your entire talk. You'll be surprised at how many things you'll have to tweak.

Additionally, virtually all talks are subject to a time constraint. DO NOT go over your time allotment! It is immensely disrespectful to your audience in two ways. First, it says that you didn't care enough to practice to make sure you came in under time. Second, it shows a lack of concern for the rest of your audience's day. So don't just estimate and hope. Practice with a timer and make sure you're in good shape.

By the way, if you find yourself skipping slides and saying "I'm just gonna skip over this because we're short on time" you've blown it. If that material wasn't important, why was it in your talk? And if it is important, your lack of practice just made you dump something that you should have covered.

Note: most talks run long. It's rare for speakers to finish early. Recognize this and err on finishing early. This will just mean an extended Q&A and/or an early finish for your audience, which usually feels like getting out of class a bit ahead-of-schedule.