Personally I would suggest going for something more safe, if he hits a low short ball and the cross court corner is open, go for a nice heavy topspin hit to that corner, and force him to step back behind the baseline, allowing you plenty of time to get to the net. Since he has to wait for the ball to come down (unless he's a diehard Agassi wannabe), he'll have more of a chance to make a mistake, and also won't be able to put too much power into it (because he has to generate his own pace). This allows an easy volley to end the point. Of course, this is only if he coughs up a short ball to you, I wouldn't suggest using heavy topspin balls (such as moonballs) for an approach shot if your at the baseline.
If the crosscourt isn't open, a possibility is to use a short low ball against him and go for a dropshot if you have the positioning and the time to do it. Otherwise, as other posters have said, just hit a low flat ball at a good angle, not too much pace.