Get an external flash unit with a diffuser instead of the built-in flash feature. These built-in flashes often make a picture look very harsh. An external flash unit gives a more natural aspect to your photographs and allows you to edit them without the noise you get when you use another kind of flash.
In most portrait photos, the subject's eyes look directly into the camera. Have your subject express a variety of emotions to capture a unique photograph. You could also try to have the people in the picture look at something in the frame.