The most common scenario with presenters with PowerPoint is on before they start speaking and never off until they are done. The projection area is always filled with an image or text that competes with the presenter. Try this technique. Do not show your first slide until several minutes into your presentation. Let the focus of attention be on you and your message. Once the audience is familiar with both, then introduce your slides. The end of your presentation should get the same treatment. End your slides before finishing your presentation. Let the focus be on you and your message as you wrap thing up.
Charles Greene III
Presentation Magician
Washington, DC
CharlesGreene.com