If you're dating a guy named Mr. Mxyzptlk, you merely have to get him to say his name backward. Otherwise, it is typically incumbent upon you to offer some word of explanation. "Bye" does not count. You should also try to avoid using a pie chart.
Do not sleep with the person right before breaking up. That can give the impression that you only did it to get one last fuck in under the gate or, worse, that you were doling out some kind of misguided mercy fuck. No one likes getting a mercy fuck, though I suppose some people like to watch them. Is there a website yet? Do not sleep with the person after you break up. This is a hard one because you still have feelings for each other, and it is so darned convenient and all. But here is what happens: just because you're sleeping together all the time, and hence seeing each other all the time, and probably doing most everything together, the ex will start getting this nutty idea that you are a couple again. I've been on both ends of that, along with times when the old college try really was attempted, and it doesn't end well. If you're lucky, it won't be the same person initiating the breakup the second time. Then you can both feel like pieces of shit. Do not break up on a trip. Sometimes you can't help but break up when you do. But if it's in the middle of a trip somewhere, particularly a backpacking trip, everyone is going to have a real bad time. Particularly if you've taken acid. Wait until you're on home territory. Go quietly into the night. If you care for the person you broke up with, you'll feel an urge to help salve his or her hurt, you know, the hurt you just caused, you insensitive prick. The shoulder that bashed his/her heart in isn't the right shoulder to cry on. Be an adult about it, and just fuck off into the sunset. And, for either of you, if things ended acrimoniously, don't seek revenge. Consider radio personality Bill Balance, who posted naked photos of former lover/professional hypocrite Dr. Laura Schlessinger on the Internet. There's a double moral there: don't do that, and don't do Dr. Laura.