Pick a quiet spot (neutral, with no fond, loving memories attached – do not break up with your boyfriend at your favorite club) where the two of you won’t be easily interrupted and be as open and honest as possible. Thank him for the time you’ve spent together and tell him the things you’ve admired about him, which really shouldn’t be that hard. Don’t dwell on any subjects guaranteed to promote arguments or bring up hurt feelings, etc. Let him know that as you’ve gotten to know one another better, you’ve come to realize that your interests don’t coincide, or you don’t have very much in common. Wish him well, and try to part as “friends.” Not friends who still continue to see each other once in awhile; but the type of friend you’d send a holiday card to. Remember, your are learning how to break up with your boyfriend.
However . . .
Assuming he’s been a cheater - some license can be taken. As much as you’d like to toss a glass of Pino Grigio in his face, or stab a fork in his eyeball, refrain . . . no matter how much effort it takes. How would that look? He’s already cheated on you and now he gets to see you (out of the good eyeball) getting carted off to jail. If you have evidence of said infidelity during your break-up discussion, put it out there; by all means let him know you’re well aware of it and infidelity is unacceptable to you. Appraise him of the fact that you’re too good for him and deserve to be treated like the queen you are. Keep it sweet, keep it short. Walk away.
Assuming he’s a Jerk or an A-Hole - the same applies. Remind him of one or two inconsiderate or unacceptable moments (don’t dredge up fifty) where his actions were totally inappropriate and irredeemable. If he says he’s willing to change and you know he is, nevertheless, think long and hard before you buy into it. One more time, this is a “break up,” which is why you should be absolutely, positively certain this is the right course for you.
If you’ve been dating a scuzz-ball, slime-bag or out and out weasel, there is such a huge desire when breaking up to get even, to settle the score, to make him feel as lousy as he made you feel. How do you get even? SMILE! Think about it; you’re doing the breaking up. You’re the one with the upper hand. Your actions say it all, that you’re no longer willing to be treated as a door-mat, and you can do better by yourself. The one thing mean-spirited people love is knowing they made someone else miserable. Take the power out of that knowledge and smile – as wide as you can. No matter what he’s done, no matter how he’s made you feel. Smile, pat him on the head, and walk away.