Mystery Machine

What would Elmo do? That question had media speculating and customers clamoring for the newest version of the fuzzy red Sesame Street character, whose holiday 2006 launch was a big secret. Maker Mattel kept mum until the doll's release in September. Once the beans were spilled, TMX Elmo became one of the year's hottest items, topping the holiday wish lists of boys and coming in fourth among girls, creating long lines at retailers who carried the doll.

"[Stealth] marketing can get customers excited about something new by building expectations," says Sheree Clark, partner at Sayles Graphic Design, a Des Moines, Iowa, advertising firm that has launched teaser campaigns. To maximize impact, she says:

Diversify. Budget your stealth campaign to invest in multiple vehicles--advertising, direct mail, e-mail marketing, PR and so on. "It has to come from several different places," Clark says.

Abridge. Mystery marketing has a short shelf life--usually a few weeks. Don't keep the secret too long or you'll lose customer interest.

Deliver. Make sure the object of your promotion has the "wow" factor. According to Clark, "If you have a big teaser campaign shrouded in secrecy but the punch line doesn't live up to the hype, you end up eroding your brand or market credibility because you won't be trusted anymore."