A few short comments
Consider using your built in flash for daylight shots of your friends. Do not rely on the flash firing automatically in daylight, just set the camera to flash. This works really well when the background is bright and your subject needs supplemental light.
Unless you want your subject to look like a prisoner, avoid straight on (face, shoulders, and torso facing the camera) shots. It is much more flattering to have your subject’s body angled at 45 degrees, close foot pointing at the camera and the other behind and pointing in the direction the body is facing. Then have the subject look at the camera or slightly to either side as you wish.
I often see Facebook Profile Photos with more than one person in them and find it quite confusing.
Have you ever seen professional models posing with their arms at their side? I have, and I think I know why. First, they are showing off the garments and accessories so the pose is less important. Second, I think, they are trying to look a bit heavier than they are. Yes, heavier. You see, when the arms are at the side, the body looks wider. Is that pose good for you? Maybe not if you possess normal body weight.
A good rule of thumb, or should I say elbow, is to bend it. One way to do this is hand in pocket or on the hip. The most slimming pose would be to make a hole between the arm and body on both sides so that the camera can see through. Now strike a relaxed, comfortable, pose, and smile. You will look great (also see my Mug Shot—Photo Tip above).
Take a look at your favorite magazines with an eye for photographs of people. Pay attention to how the person is posed and put yourself in their place. Rip out the ones you like best, and try to copy the pose. Share your rip sheets with the photographer.