Presenter view - your screen's different from the audience's

PowerPoint has a smart little-known feature built in: presenter view. The screen on your laptop is different from the full-screen view the audience sees.

1. Slide count
2. Current slide
3. Notes
4. One slide back
5. Marker
6. Opens a menu (black screen, white screen, other functions)
7. Next slide
8. Presentation timer
9. Slide sequence

In order for it to work, you need to setup your computer for 2 monitors (The primary monitor is your laptop, the second one the big projector) in windows control panel/display properties. After that, in the PowerPoint slideshow menu, set up slide show and go to the multiple monitors section.

UPDATE: From the comments below, John Goalby is pointing to his very detailed, free ebook on the subject of Presenter View.