Lisa Lerer, 09.25.06, 6:00 PM ET

We've all heard betrayal stories: The husband discovers an e-mail between his wife and her boyfriend, the boss catches an employee at lunch with a competitor, the politician lies about, well, everything.

From love to business to politics, trust matters. There's no magic formula to building a trusting relationship. But there are a couple tricks to help you gain trust in a hurry--even if you don't deserve it.

The first step is simple: Seem like someone people trust. Harvard Business School negotiations professor Deepak Malhotra suggests giving references, which can serve as live testimonials to your abilities. Just be sure that your references trust you first.

If you're short on friends, propose setting milestones, says Malhotra. For example, if a client is reluctant to sign an exclusive contract, offer a short-term nonexclusive deal first. After you've proved your competency, your partner will feel more comfortable committing to the exclusive agreement.

Going slowly also helps earn trust in romantic relationships, says dating coach Patty Feinstein, who often advises her clients to keep things casual until they get to know each other better.

Credentials are useless if not backed up with know-how. Philip Reed, consumer advice editor for the automobile shopping Web site Edmonds.com, spent six months undercover as a car salesman at two different dealerships. During his training, the salesmen told him to always have a response to every question. And if you don't know the answer? "Either tap dance around it or make up what you believe to be true," Reed says.

Of course, if the customer discovers you are lying, all trust will be broken. "Car salesmen and real estate agents sometimes overdo it," says Malhotra. In her 2004 study on deception, University of California, Santa Barbara, psychology professor Bella DePaulo found that liars rarely admit mistakes. So, if you want to seem truthful, confess your ignorance. (This tactic didn't work for Reed, who came clean when he couldn't answer a customer's question. The writer-turned-salesman sold only five cars in six months.)

Maybe he should have worn a short-sleeved shirt. Feinstein encourages her clients to bare their forearms and show their palms. Flashing some skin indicates openness and availability. Eye contact is also key. If you're looking away, she says, you seem shifty.

But body language isn't universal: In some African countries, looking your boss in the eye is considered disrespectful. Conscious of these kinds of cultural differences, intelligence agents are trained in local cultural mores before they take a post abroad, says Peter Earnest, director of the Spy Museum in Washington, D.C. Earnest, a 20-year veteran of the CIA's Senior Intelligence Service, believes that trust happens on a subliminal level, so niceties matter.

"They may not know why they don't trust you, but they'll know something is not sitting well with them," he says.

The same idea applies in different business cultures, which often have their own lingo, says Malhotra. Several years ago, an airline invited a bunch of consulting firms to bid on a contract to build a new, high-tech ticketing system, he recalls. Everyone at the meeting was using the word "lifts." Feeling lost, a representative of one firm asked for a definition. The room fell into silent shock. A lift, it turned out, was the standard industry term for a paper ticket. The firm obviously didn't get hired. If you don't understand industry terms and acronyms, says Malhotra, you won't seem trustworthy.

Old-fashioned kissing up can also encourage trust. Feinstein advises her clients to make the object of their affection feel at ease by doing favors, giving compliments and being accommodating.

The key to establishing a long-term connection is consistency. A key part of espionage, says Earnest, is making local informants feel safe in every situation and with everyone in the agency. "If someone else is sloppy," he says, "the source fades away."

Or, to put it more simply: If you want someone's trust, call when you say you're going to call, and show up when you say you're going to show up.