Decide how the camera will be used. Will you use a tripod or hold the camera in your hand? For a standard yearbook portrait shot, a tripod is a must, while an action photograph is best taken off the cuff without encumbrances.
Set up your shot. For a portrait, consider a backdrop screen for your subject, preferably something plain that won't look dated in years to come. Natural light should be removed from the equation when taking a portrait photograph so you can fully manipulate lighting with your flash.
Set white-balance and shutter speed. Depending on the lighting in the room, you will need to adjust your camera's white-balance for fluorescent or incandescent light bulbs. Shutter speed should not be a major concern, as your subject will be sitting still, but find a setting that does not allow too much light in while preventing blurring.
Take practice shots. On the morning of the shoot, have a friend sit in as a test subject. The advantage of modern digital cameras is that you can take as many practice shots as you need without worrying about wasting film stock. Find a good set up and stick with it for the shoot proper. Make notes if it helps.
Review your settings as the shoot progresses. With a good practice set-up, you should not have to make many changes. However, people with extremely light or dark skin tone might require a slight adjustment in shutter or flash settings so they don't appear washed out or too dark.
Speak to and reassure your subject. Often people are very nervous on yearbook photo shoot day, so try to relax them with a joke or a polite comment. If your subject seems nervous or tense in a photograph, try to direct him so he appears relaxed. Obvious signs of tension include raised shoulders and tight facial muscles. The advantage of digital photography is that you can see pictures immediately after they are taken. If you notice something that might embarrass a shy subject, take another picture of her. Also consider showing your subject his photograph afterward so he can request another if necessary and not have to just worry about his shot until the yearbook is published.