Never stop testing, and your advertising will never stop improving.
David Ogilvy (1911–1999) US “Father of Advertising”
Test your presentation! First of all check to see if all the slides are in the right order, that your animations (if you use them) are working properly and that the presentation works on the computer system you are going to use.
Second, test it for the timings, intonations and possible questions / misunderstandings together with another person. Go through the whole presentation as if it were the real thing. Steve Jobs, the Apple CEO, used to rehearse for 48 hours with a selected audience. If you don’t have anyone nowadays Smartphones are useful helpers: film yourself and review yourself critically.
Third, testing of the technical equipment (cable connections, batteries, settings of computer in connection with data projector etc.) is also crucial. Don’t forget to schedule this time (and forget that many participants show up earlier and you won’t have the time to fix technical things when they arrive).
Fourth, watch out for the No-go-area, i.e. where you shouldn’t stand or walk in order not to block the audience’s view on the screen.