Tell him things that you're thinking. They don't have to be long. A lot of guys don't have the attention span to read a whole story while there at work, or in class, or whatever. A quick text of how turned on YOU are or somethign that you'll do to him the next time you see him, is a GREAT way.
giving him a play by play on exactly wut it is ur gonna do to him =]
Erotic Stories. :D Works like a charm!
tell him what u would do to him! lol