The knack: How to start an urban myth by Rick Glanvill

"Credible fallacy, that's the key. First of all, acquaint yourself with the nuts and bolts - public humiliation, social inadequacy, sexual taboo, superficial details. Social climbers are easy targets - think of narrowly avoided public humiliation involving illicit sex, bad toilet habits or over-enthusiastic animals and extend it through several twists to the ultimate nightmare. Then say it happened to someone in the marketing department - `not sure who'. People will want this sordid episode to be true. There's nothing more comforting than laughing about someone else's misfortune - the bread and butter of the urban myth.

Choose your moment. The well-oiled dinner party is a fine platform for your myth to make its bow. Time your delivery so that conversation moves almost seamlessly from their hard fact to your floppy fiction. The pub is even better, as people go there to lose themselves, or make themselves feel better. The more adventurous might like to invent a suitably undermining myth around a smug celeb. Don't Gary Barlow or Gaby Roslin deserve a few smears on their squeaky clean facades?

New technology is always a handy handle too - for example, `those satellite dishes, one bloke fitted one at the wrong angle and it concentrated the sun, burning his neighbours' curtains'. Think hard enough and a terrifying `home truth' about interactive digital TV or the Internet will present itself. In fact, the Internet, one of the finest sources of urban legends, is a great place to hone your craft. Post a message at somewhere like www.urbanlegends.com and watch it spread like conversational canker."

Rick Glanvill is co-author with Phil Healey of `Now! That's What I Call Urban Myths' (Virgin Publishing, pounds 4.99)