How do you get a guy to stop flirting with you?

[RiddleMeThis]

Seriously dont listen to anyone who is saying be negative towards him. It will just end badly and you will have to live with it.

If you really dont want to be mean, and you would like to be able to have say Hi to the guy while passing in the street without feeling bad, then you need to tell him how you feel.
You dont have to go into much detail, just make sure the next time you see him (not over facebook or whatever-we live in a real world) wait until you are alone (preferably) and tell him that you like him as a friend, and respect him as a human being, and that is WHY you HAVE to make things CLEAR that NOTHING relationship-wise is going to happen. Say this with a slightly uneasy smile and eye contact. After you said this take a slight pause then say OK? When he says ok, hold your hand out and say Friends? Then shake on the DEAL you just made!

Well Done You! - Situation sorted with no negative backlash! What a brilliant person you are!

That is what you must do.
It will work, because he is Male, and something you have done without noticing has told him that there maybe still a chance with you thats why he has started again, and now you just made it clear. Nicely!

Obviously if he persists again after this, just cut him off completely.

Good Luck and Hope this helped!