The Invasion: An acquaintance greets you with an unwelcome bear hug or a slobbery kiss.

The Defense: Head off advances with your body language. “You should put out your hand long before the person gets to you, so he knows you prefer to only shake hands,” says Hector Garcia, a bodyguard with Valle Security International. Or take a cue from the way people deal with uncomfortable closeness on subways and buses, says Robert Sommer, professor emeritus of psychology at the University of California at Davis and the author of Personal Space (Bosko Books, $20, www.amazon.com): They treat other passengers like trees. “Go rigid, avoid eye contact, look away, and act busy,” he says. If it’s too late to stop an affection attack, use humor to make your feelings known. “Draw back in mock horror and say, ‘You know, I’ve given up kissing temporarily, at least until after I’ve had my flu shot,’” says Letitia Baldrige, author of New Manners for New Times (Scribner, $35, www.amazon.com). “You are obviously joking, but he’ll get the message.”

Most important, express yourself early on, advises Ceri Marsh, coauthor of The Fabulous Girl’s Guide to Grace Under Pressure: Extreme Etiquette for the Stickiest, Trickiest, Most Outrageous Situations of Your Life (Broadway Books, $15, www.amazon.com). “It’s tough to break habits that have already been established,” says Marsh. “Once you’ve agreed, even tacitly, to the kiss-kiss hello, it’s very tricky to move to the handshake.” Her suggestion: “Try standing slightly farther away from this person when you greet him next,” and angle your body so you’re not meeting him head-on.

The Invasion: An office mate is constantly in your cubicle, reading over your shoulder or picking up papers from your desk.

The Defense: You’re there to work; that’s the only excuse you need. And while offices aren’t exactly homes, they should be treated with the same kind of respect, says Lois Frankel, an executive coach and the author of Nice Girls Don’t Get the Corner Office (Warner Business Books, $20, www.amazon.com). “You wouldn’t think of going into someone’s home uninvited, picking up their mail, and reading it,” says Frankel. “And the same courtesy should be extended in the workplace.” She suggests posting a lighthearted sign to indicate when people are welcome to come in or to designate desk items as off-limits. “Something to the effect of ‘Unless you plan on cleaning this desk, don’t pick anything up!’” says Frankel. “If the culprits still don’t get it, try saying, ‘Can I help you?’ or ‘Those papers are private.’”

Of course, in a cubicle, you’re a sitting duck. Sommer suggests personalizing your work area, whether it’s with a few family photographs or a distinctive plant. Establishing it as your private space can subtly reinforce boundaries and help fend off overfriendly office mates.