Once you tap Play, you can use your iPad to control the presentation as well as provide presenter notes for yourself (a cheat sheet, if you will) that the audience won't see. To change what's on the iPad's screen when using an external display, tap the Layouts icon and then one of the follow buttons: Current (the current build of the slide as shown on the external display), Next (the next build, which may or may not be the next slide), Current and Next (current and next builds side by side), or Current and Notes (current build and any accompanying presenter notes). This final layout is the only one to display presenter notes, but you can supplement it by tapping the button in the upper left corner to display a list of slide thumbnails, which can aid in navigation (tap a thumbnail to jump directly to that slide).
(Image Caption: In Keynote's Current and Notes layout, you can see presenter notes underneath your slides. The thumbnails on the left are optional.)
To advance to the next build or slide, tap once anywhere, or swipe toward the left. To go back, swipe toward the right. A nice extra in Keynote for the iPad is a "laser pointer": Touch and hold on the iPad's screen to show a red dot, which moves with your finger on the main display. Lift your finger and the dot disappears. This is useful when you want to call attention to a particular area of a slide. To end the presentation (and turn off Keynote's video output), tap the Close icon.
(Image Caption: To highlight a particular word or image on a slide in Keynote, use the simulated laser pointer.)
If your iPad is physically connected to your display--or if you want to be able to move around during your presentation without carrying the iPad with you--you can download Apple's Keynote Remote app ($1) on your iPhone or iPod touch. Follow the instructions to pair Keynote Remote with your iPad using Wi-Fi or Bluetooth, and then your iPhone or iPod touch becomes a remote control for Keynote on your iPad, complete with previews of your slides.
Senior contributor Joe Kissell is the senior editor of TidBits and the author of the ebook Take Control of Working with Your iPad.
[Editor's note: This story has been updated to include information about iCloud, AirPlay, and the third-generation iPad.]