PowerPoint is a brilliant visual aid, but only when it is used correctly.
Traditional use of PowerPoint stifles discussion and critical thinking, and dulls focus. It's boring. Slide after slide switches audiences off, steadily reducing their ability to take in information. You are wasting your time - and theirs.
At first this might sound trivial - you push the B button on the keyboard (or the black screen button on the remote) and the screen goes to black. you push it again and it returns to the picture you had.
It's not trivial. This tip has a lot to do with your presentation credibility.