I normally arrive at assignments at least a half hour earlier than the earliest I think I think I'll need to be there. This often leaves me sitting with nothing to do (sometimes for hours), but it always gives me plently of time to get set up and checkout wherever I'll be shooting. I use the time to check out different areas that I think I'll be shooting in, and figure out my exposure for each of them. I normally meter the scene, and shoot a few shots, normally right from the hip without looking. I've found recently that I really enjoy some of these test shots when I see them on the computer later.
The image below is one of those random shots.