Make certain you know how to use all the equipment required for your presentation including what to do should any item malfunction. The time you take to learn and practice will be repaid by a smooth and satisfying performance. Using part of your presentation time to figure out what just went wrong and what to do next not only will distract your audience but also is likely to leave you flustered and prone to make other blunders. Electronic aids can be a wonderful enhancement for virtually any presentation. They also are a prime target for Murphy's Law if anything can come unplugged, it probably will