How to do it: Chances are, she doesn't expect a big explanation. Be blunt and tell her you're not looking for a relationship. If all else fails, keep a poorly hidden, framed picture of another woman close to your bed, jokes David Blend, editor of Thrillist, a men's e-newsletter in New York. "When your hook-up confronts you, you can claim she's your girlfriend, even if it's really your sister."
Why it will work: Your hook-up was about sex, not feelings, so it's OK to make a clean break with minimal fuss.
What to watch out for: If the evening ended at your place, it can be tricky getting her to leave. If she suggests breakfast, tell her your mom's already on her way over to pick up your laundry-that should get her out the door in a hurry.
How to do it: A phone call is ideal. Just make sure you keep it short and sweet. "As much as you may want to, don't just stop calling," says Alison James, author of the breakup manual I Used to Miss Him . . . But My Aim Is Improving. Tell her you had a great time but you're not feeling a long-term connection. "Your honesty will save her (and her friends) from endless hours of 'What the fuck happened?' analysis"-and you from the drunk-dialing following their all-night bitch session.
Why it will work: Like ripping off a Band-Aid, it only stings for a second. Plus, by using your cell, you won't have to see that pained look on her face when you tell her it's not going to work.
What to watch out for: The chick who wants to stay in touch. It's cool if you're up for it. If not, let caller ID and voice mail save your ass until she finally gets the hint.
How to do it: At this point, you've got to go face-to-face. Pick a quiet, neutral spot, such as a coffee shop or a park, to minimize the possibility of a scene. "Say you don't think you're right for each other but that you had fun getting to know her," says relationship expert April Masini, author of Think & Date Like a Man. She'll be pissed if she wants more, but if she doesn't, she'll be relieved.
Why it will work: She'll appreciate that you're being mature and not pulling the old disappearing act.
What to watch out for: A repeat of Fatal Attraction.
How to do it: "However you work up to it, the most important thing to do is make sure she gets the message the breakup is permanent," says James. "It's going to crush her no matter what, but you'll gain your freedom faster if she knows there's no chance you'll have a change of heart."
Why it will work: By making it clear that you two don't have a future, you're sending a message that can't be misinterpreted. If necessary, place the blame on yourself. It'll give her a target for her anger, and the more she can channel it, the faster she'll be willing to accept things are over-and erase you from her MySpace page.
What to watch out for: Flying vases and dishware. If the breakup comes as a complete shock to her or if you've cheated on her, be prepared for a very pissed-off ex-to-be. Expect massive tears or a revenge attack-so make sure you grab all your most prized possessions on the way out, just in case she decides to whip out the chain saw or a can of gasoline.