Use your hand or pointer and point to items of interest on the screen . Do not, in general, cover half your transparency to create suspense. For some people, this technique only creates annoyance. Gesticulate for emphasis only. Pace your delivery.
Silence is, in fact, useful when asking a question.
Answer Gives audience time to think of an answer themselves. Vocal delivery also affects attentiveness. Speak normally, then at crucial point lower voice or speak slower. Introductions and Conclusions are the most important. Research shows audiences listen more at the beginning and end of a presentation.