Games : How can I effectively approach stationary targets in supercruise?

A lot of the time, I find that I'm overshooting my targets in supercruise. I don't want to approach too slowly, because I still want to get there within an hour, but I also don't want to overshoot and have to turn around and correct course. About where should I set my throttle to ensure I slow down in time to disengage at my target when in supercruise?