I guess you first need to think about whether you actually want to end your relationship, or if you're just a little bored/pissed off with him. Ending what is basically a great relationship for those reasons is a sure fire way to get yourself into one of those horrible 'on again/off again' situations. If you do want to split with him, do it to his face. Line all your reasons up and be prepared to stand your ground if he wants you to try again. Keep calm and empathise with his feelings, but be strong. Don't name call, just tell him your feelings for him have changed and you don't want to string him along. Finally, accept that he's going to be upset, these conversations very rarely end with the injured party giving you a hug and wishing you well, but he will appreciate your honesty and compassion in the end.