That sounds like a plan but in practice that is a) quite a harsh blow to your self esteem if you're on the recieving end of that and b) may not nessercaily deter said person if they are that into you (I've had a case where some crazy girl tried to break up me and my girlfriend at the time because she had, I'm going to be generous and call it a crush rather than an obsession, on me).Souplex said:Drop your boyfriend into a conversation. Boom, any attraction he feels will melt away instantly.
My personal reccomendation would be just be friendly yet neutral towards them until they try making an advance on you, at that point, outline the fact that you are simply not interested in a romantic/sexual relation with them (make it explicit but not brutal if you know what I mean).