northwest,
Other members will have more specific advice, but here's my crack at answering "What would I say?":
"Hello, Coach Lastname. This is Joe Playername, and I noticed that you were at my game Tuesday night. I'm very interested in NameOfSchool University, and wondered if you have any feedback for me."
Then you can let the coach talk, because he has done this MANY more times than you have.
You can listen, then answer any questions he asks you. Before the call you might write down 1 or 2 questions that you can ask him at the end of the conversation if he asks "Do you have any questions?" Asking whether you should send your summer schedule could fall into this list.
Good luck... it certainly seems like a positive sign that he was at your game!
Julie