As you become more experienced, you will learn how to use depth of field to your advantage. For example, at the telephoto end of the zoom range, the shallow depth of field can be used to throw a busy background out of focus while keeping the subject sharp as a tack. Conversely, wide-angle shooting usually keeps everything in front of the camera in focus. When events are happening quickly and you don't have time to pull acurate focus before exposing film, shoot everything in wide angle. Your footage will, at the very least, be in focus.
Composition is a crucial tool for communication with film.
Look through your viewfinder and see everything that's in the frame. Don't always put your subjects in the very center. The composition in the bottom of Figure 1 is visually more exciting than the top composition because the subject is off center. Never let the horizon cut the frame perfectly in half. Put it above or below the midway point of the image.