Be prepared for any problems. While it is unlikely that you will encounter problems, it’s best to have a game plan. If you are using PowerPoint, have an alternative if the computer dies (arrange for a back-up machine) or the projector bulb burns out (makes sure the technical staff has an additional bulb). You should be prepared to give your presentation without overheads if worse comes to worst. Some speakers keep handy an outline of their talk on 3X6 cards as a back-up if there are technical issues. Being prepared for a worst-case scenario should make you much more relaxed.