I doubt there is a consistent answer to this one, everyone has different preferences. For me, it varies depending on the car and how good the cockpit view is. Some cars have obstructed cockpit views, so that is where Camhack is very handy, then I do what Aaron describes, move the camera until I get a better view of the road.
I doubt anyone with a wheel would use Swingman view (behind the car), it would feel totally unrealistic and difficult to get used to. The bumper view gives the best view of the road, but it is much easier to hit banks etc because you don't know where the edges of your car are.
Again though, to each his own.