Composition for video is basically the same as it is for graphic design. Simply put its all about where you place the elements on the screen so it's visually appealing for the viewer. As you can tell from this opening you either have great composition or you don't.
A basic rule about composition is called head room. Head room is leaving enough space above your head. Most cameras have guide frames to help you out with this. Just remember to keep your guide frame on top of your head and you'll be alright.
Now lets take our talk about composition one step further and talk about the rule of thirds. The rule of thirds is simply dividing the screen visually both vertically and horizontally into thirds. Now place your subject on anyone of the intersection points and you have great composition. Typically in video we use the top two intersection points. This is commonly referred to as either framing on the right or framing on the left.