First of all, it all depends on the degree of closeness of your relationship. If you haven't met with the guy and nothing he promised, the correct style of behavior – a demonstration of complete indifference. Try to look aloof in his presence and be sure to follow with your body language. Do not turn in his direction, do not show your openness, don't look him in the eye and, especially, don't touch him, even accidentally, if you still have to speak.
Your failure must be categorical. Therefore, no smiles and jokes. Remember that you should out of courtesy to keep him talking, and for a young person this could be a signal to continue the contact.
If you act insecure, your behavior may be regarded simply as the fatten themselves prices or breaking. So the guy is likely to make an attempt for you to strengthen the pressure and will triple my efforts to start taking care of you, because any member of the opposite sex is by nature a hunter.
Should not be too aggressive because you don't know this person and can't imagine his response. If you don't want trouble, you should try and make a failure in a firm but polite manner.
If you have already tried to meet the guy and after some time realized that it's not yours, and you should this relationship terminate, the line of conduct is built differently. First, it is best if you're honest and forthright. Why to fool a decent man who, like you, can happily arrange his fate? Tell him honestly that you really regret what you're saying, but otherwise can not do that, he's a good guy, but the feelings of order impossible. Say so that he had no hope that in the future the renewal of your relationship possible. Ask him to remain a friend. It is unlikely that he will immediately agree. But when it will take some time, sharp feeling of resentment go, and he is aware of the fact of the rupture of friendly relations is possible.
In a difficult conversation can help a sense of humor. Turn the situation so that your boyfriend wasn't offended and laughed. It is, of course, upset, but a bad aftertaste in his soul will surely be less.
With touchy, proud, and insistent a fan to say especially hard. So you better think about the words you are going to say in advance. You should not start the conversation if you are angry and can't cope with them. And, of course, during a call, you should not spare fan or respond to his provocations. Be firm, sincere and straightforward. In the future the guy will appreciate it.
Make sure that the young man went from you myself. There are several ways to make this possible. First, the "debunk" myself in his eyes. If you know what he appreciates, try to make it clear that you're not. Secondly, show excessive persistence. Bother him for any reason. Show too much attention and try to control every minute of his life. Thirdly, check for "lice". Show that you have a lot of problems in life, from the moral to the material, and what you hope to "settle" them. Moreover, if you realize that you are not very serious, you can "finish" him with his matrimonial plans. Hint that you now expect from him the submission of the application to the Registrar.