Don't try too hard to be cool. He already thinks you're cool. Nine is fine. If he's not huggy or touchy, don't be offended, he still loves you. If he is, don't read sex into it.

Don't drink or do drugs when you're around him. If you ever have impulsive or needy moods, be very cautious. If you're not sure you can trust yourself, never meet just one-on-one. Keep other people involved in any case, especially his parents - stay in public a lot, make sure everything you do would look good if seen and make a good story if told. If you have sexual tension before he comes by, get rid of it first by doing like Ben Stiller in There's Something About Mary (except the part about the hair). If you have no idea what I'm talking about, search on the movie name in the Urban Dictionary.