When he hits you (or anyone else), gently take both of his hands in yours and look directly into his face (on his level) and say "no hitting" or "we don't hit, that's not nice". You have to be consistent and use the same response EVERY time. It will probably take a little while, but he will get it. I usually recommend ignoring behaviors that you want to quash at this age (such as tantrums or screaming), but you can't ignore hitting because it will inevitably get worse and you can't chance that he will hurt another child. Good luck to you! This is just a phase, so it will pass, don't worry.
Updated comment - I read some of the other posts and I would also encourage baby sign language as one poster suggested. I taught it to my daughter starting at 7 months and she picked it up right away. I have started signing to my son also who just turned 6 months. They don't get quite so frustrated because they are able to "tell" you what they want/need to a certain extent. Anyway, I highly recommend trying it.