Science backs up what the etiquette books have been saying all along: A firm handshake helps make a good first impression for both males and females. A July 2000 University of Alabama study found that consistent with the etiquette and business literature, there is a substantial relationship between the features that characterize a firm handshake (strength, vigor, duration, eye contact and completeness of grip) and a favorable first impression.

"Handshakes are the only consistent physical contact we have in the business world. They happen first, so they set the tone for the entire relationship," says Jill Bremer, a professional image consultant and co-author of 'It's Your Move: Dealing Yourself the Best Cards in Life and Work' (Financial Times Prentice Hall). "People make an immediate judgment about your character and level of confidence through your handshake. I have participants pair up and try all sorts of "bad" handshakes -- wet noodle, fingers-only, bonecrusher, two-handed, upper hand - then teach them the right way to do it." Here are some tips from the experts on the perfect handshake.

Be a mover and shaker.
It is appropriate to shake hands in any public business setting -- job interviews, business meetings, thank-you gestures. The proper handshake should be firm, with an energy that communicates sincerity, strength and professionalism, says Dianne M. Daniels, a certified image coach and author of "Polish and Presence: 31 Days to a New Image." The perfect handshake is one that conveys a friendly, welcome attitude. "Generally, the person who extends their hand first has the 'power' in the setting," says Dr. Nancy B. Irwin, a Los Angeles-based psychologist and therapeutic hypnotist. "In our American culture, the handshake shows interest, openness and confidence."

Put them in the palm of your hand.
Dale Webb and Pauline Winick, founders and directors of the Protocol Centre in Miami, Fla. stress the importance of having proper form. Extend your arm with your hand outstretched with thumb straight up. Make sure hands are web-to-web -- slide your hand into the other person's until your webs touch. Give it just two pumps.

Get a grip.
Limp, lifeless handshakes tend to communicate timidity, passivity or intimidation. The "limp fish" and "barely touching" handshakes project a sense of distance and a "don't touch me" attitude, says Daniels. It's hardly welcoming and no one, including women, is exempt from this rule.
Handle it with gloves. When shaking hands with a more mature person than yourself, Daniels advises to be careful not to squeeze the hand you are offered too tightly -- it could cause pain. This also applies to not rapidly or strongly pumping their arm, as you could cause injury. Many people have allergies, sensitive skin or fragile bones due to health issues, such as carpal tunnel, adds Irwin.

When to go hand in hand.
When shaking hands to congratulate someone, Irwin recommends the double handshake. This is when you "glove" or "sandwich" the other's hand with both of yours and indicates pride, warmth and sharing. "This can overpower or threaten some people," says Irwin, "so one must be careful and use this when they know someone well."

Be a right-hand man or woman.
In today's business environment, both women and men shake hands. The idea of a man waiting for a woman to extend her hand first is outdated, say Webb and Winick, and a woman should extend her hand. What about men? "Save the 'I'm stronger than you' type of grip for non-business situations with friends or competitors," says Daniels. "Exerting yourself to give a stronger-than-normal squeeze to another man is not the way to show your dominance, and can set a confrontational tone for the rest of your association."