Background key / matte...

Imagine you have a few shots of people in front of a standard photographer's white backdrop, but at the sides of the shot you can see all kinds of clutter that are not intended to be in the shot. What are the best ways of removing unwanted information from the picture? Basically I'm trying to get that 'Gap commercial' look - with an all white background from an image that has a partly white background...

Probably the easiest method would be to load the clip in the viewer, then go to the Motion tab and use the crop tools to cut off the edges that you don't want.

Once you have clean edges, slip this clip up to V2 on the timeline, and then put a colour matte (from the generator that looks like a capital A on the bottom right of the viewer) on V1. Load the colour matte into the viewer, and hit the Controls tab. Now use the small eyedropper you find there to select the white background in your canvas to get a match. You may need to mess with the matte a little depending on your lighting.