Flicking (Drag) is how you advance to the next picture in the batch. Flick from right to left. (Flick from left to right to view the previous photo.)

Zooming a photo means magnifying it, and it's a blast. One quick way is to double-tap the photo; the iPhone zooms in on the portion you tapped, doubling its size.

Rotating is what you do when a horizontal photo appears on the upright iPhone, which makes the photo look small and fills most of the screen with blackness.

Just turn the iPhone 90 degrees in either direction. Like magic, the photo itself rotates and enlarges to fill its new, wider canvas. No taps required. (This doesn't work when the phone is flat on its back—on a table, for example. It has to be more or less upright.)

This trick also works the other way—that is, you can also make a vertical photo fit better when you're holding the iPhone horizontally. Just rotate the iPhone back upright.

Another way is to use the two-finger spread technique (Pinch and Spread), which gives you more control over what gets magnified and by how much. (Remember, the iPhone doesn't actually store the giganto ten-megapixel originals of pictures you took with your fancy digital camera—only scaled-down, iPhone-appropriate versions—so you can't zoom in more than about three times the original size.)

Once you've spread a photo bigger, you can then pinch the screen to scale it down again. Or just double-tap a zoomed photo to restore its original size. (You don't have to restore a photo to original size before advancing to the next one, though; if you flick enough times, you'll pull the next photo onto the screen.)

Panning means moving a photo around on the screen after you've zoomed in. Just drag your finger to do that; no scroll bars are necessary.