I'd show him a forehand grip and a backhand grip, but don't spend too much time on it at first. Just make sure his hands are somewhere in the general vicinity of where they should be. Many beginners don't even hold the right part of the handle. Keep his hands near the butt, unless his racquet is too long or heavy for him. Spend more time on the stroke itself. Make sure he turns sideways, perpendicular to the net, and takes the racquet back low below the path of the ball. Try and emphasize hitting the ball out in front, (start him off sideways, tell him to hit the ball out by his front foot) and make sure the follow through comes up nice and high at the end. You're gonna have to just get a feel for the kid. If you can sense that he's really into learning this stuff, you can get more technical and pound the details in a bit more. The challenge is the keep the kid entertained and having fun. If they aren't having fun, they won't focus/listen, and won't retain anything you say!
Something he might have some fun with is...if you start him out in ready position near the middle of the baseline (or move him forward if he can't hit it that far), make him run to one side and hit a forehand...then make him run to the middle, then to the other side. You're going to want to toss him the balls, don't hit them to him, they'll come too fast most likely.
Volkl Tour 10 V-Engine MP