*DON'T TURN OUT THE LIGHTS IN THE ROOM. This implies that the visuals are more important than you, and that's not a good message to send. You may have to sacrifice the readability of your visuals a little - although most projectors today are very bright and allow great visibility of slides - but it's still better to sacrifice the visibility of your slides instead of you.
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*DON'T RUN A CONTINUOUS SLIDE SHOW. Let go of the need to have to have a visual up all the time. Go to black from time to time, either by blacking out the screen with the remote or with the B key on keyboard or by inserting the occasional black slide. This is a powerful technique that prevents PowerPoint overload and allows some of the focus to shift back to you.

*END ON A BLACK SLIDE. This is a nice way to end your presentation-nothing on the screen to distract from you during your close or the Q&A session. Leave your black slide there and don't exit the "Slide Show" mode until you are completely done with your presentation, ready to leave. If you exit Slide Show before you're done, the audience has to look at the "Slide Sorter View" of your program, which is busy and distracting.
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*FINALLY, MAKE SURE YOU CAN GIVE YOUR TALK WITH IT. Stuff happens -- light bulbs blow out, the computer crashes, there's no electrical outlet to be found. Don't take up your presentation time fiddling with the equipment or bemoaning your bad luck. Go forward as if nothing's amiss. If visuals are crucial to your presentation, have hard copies on hand to distribute so that your audience will have something to refer to.

Your slide will now be black and when projected in a room, will simply look like there's nothing on the screen. A great opportunity for the speaker to capture the focus!

There is another trick that will create a dark screen. If, while you're in "Slide Show" mode, you hit the "B" key on your keyboard, your screen will go dark. When you hit it (or the mouse or the arrow or enter key) again, the visual you had darkened will come back up. (Please note that this feature works only in "Slide Show" mode.) Now, before you get all excited and think, "Great! I'll just use the 'B' key to go to blank in between some of my slides," let me offer a word of caution.

First of all, the thing about the "B" key is that when you hit it the second time to get out of the black slide, it doesn't advance to your next slide. The visual you had up before the black slide will reappear. So it's going to be awkward to have to bring up your previous slide before you can go to your next one. Secondly, what do you think the likelihood is that you're going to remember to hit the "B" key after certain visuals? It's risky to rely on your memory. It's much simpler to just insert a black slide when you don't want anything on the screen.
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