In my kids’ tennis class they are getting good enough to have actual rallies.  The coach feeds them a ball and has them play out points.  Each rally is worth 1 point and they play to 10.  To stop them from trying to hit winners on the first shot and in attempt to get them to play longer rallies, the coaches tried out an interesting rule.  “The ball must cross the net four times before the point begins.  If your shot goes out before that, its 2 points for the other side.”