Revenge 101: Don’t Get Mad, Get to Class : New York: Night school offers instruction on striking back. But don’t forget libel insurance. You might want to get a lawyer lined up now.

Want to get revenge on a cheating spouse? Wash his underwear with fiberglass and give him a really nasty itch.

Sick of lousy service? In place of a tip, leave a few drops of a chemical so foul-smelling the restaurant will have to close for weeks.

Need more ideas for getting back at a noisy neighbor, a nasty co-worker or a no-good girlfriend? Try taking a night school course on “Getting Even” offered in New York, where turning the other cheek is unsatisfying and forgiving and forgetting is no fun.

The class is taught by seemingly mild-mannered Philip Seldon, a food and wine expert by trade. Seldon is a man to be handled with kid gloves, who by his own account has exacted revenge on business rivals, neighbors and even bullies from his childhood.

His philosophy - and the reason he says he offers the class - is that revenge is a healthy cure for anger. “A great way to get it out of your system is to plan to get even,” he said. “You can go to sleep with a smile on your face because that person is going to wish they never met you.”

Some students at a recent class looked determined to follow that advice. One was a bearded man who would say only that he wanted to hire some women to help him humiliate someone who had done him wrong. Another was a wild-eyed woman who complained of losing a lot of sleep and some of her sanity from living over an unrepentantly noisy restaurant. Three women in the back row, apparently more light-hearted types, insisted they were taking the class as a lark, but their eyes lit up at suggestions on how to settle scores with ex-beaus.

None of the students was willing to reveal a name.

Tops on Seldon’s list for getting revenge is printing up posters or handbills, which he says are largely protected under freedom of speech laws, denouncing the offender. Stick to the facts and use only descriptions such as “screwball” - which he contends is libel-proof because no one can say what it means. Whether a judge or jury would agree with his legal interpretation is, well, subject to interpretation.

He also offers a list of insults to be spat out at the deserving and the telephone number of a company that sells the malodorous chemical for clearing a building in seconds. And he suggests planting tidbits about business rivals in local gossip columns--truthful tidbits, presumably, to avoid libel laws--or informing authorities if someone cheats a bit on his or her taxes.

Send every stitch of an unworthy mate’s clothing to the dry cleaner - particularly one across town. Complain to the sanitation department about recycling at your apartment building and even the most tidy landlord is likely to get slapped with a fine.

Seldon says he emphasizes revenge that stays on this side of the law. Letter bombs are out, sending pizza deliveries is a no-no and signing someone up for junk mail is taboo. No changing someone’s door or drawer locks and no smearing a windshield with petroleum jelly either. And that malodorous chemical? Hmmm...

“Some things he told us not to do I’ve already done,” confided the woman waging war with the restaurant downstairs. “So I’ll be a little more cautious.”

But since even the best-laid plans can go awry, Seldon can also suggest the name of an insurance company that offers coverage against libel.

Exacting revenge requires biding your time, planning carefully and staying closemouthed, Seldon stresses. And not all problems can be solved by revenge. One woman was visibly crestfallen by Seldon’s complicated suggestion that she trap her ex-husband with another woman and videotape the affair.

“Everything else I can think of with ex-husbands is illegal,” Seldon admitted. “That’s the problem with a lot of things.”