As more politicians get ready to hit the stage during the presidential nominating conventions, they should be cautious about what they say -- and what they don't. Body language can speak volumes.
Whether it's blinking too frequently (a sign of discomfort) or gesturing frenetically (a sign of dishonesty), body language analysts say that perfecting the text of a speech is only one of many hurdles good speakers must master before approaching the microphone.
One man who has become somewhat of a public speaking guru, according to Greg Hartley, a former Army interrogator and author of "I Can Read You Like a Book," is former President Clinton, who spoke Wednesday evening at the Democratic National Convention.
"Bill is a pro," Hartley said. "He uses his face and hands to draw people in to what he's saying."
Hartley, who watched the former president and the Democratic vice presidential nominee Joe Biden speak, said that Biden's authenticity was shown through something as seemingly insignificant as his lips.
"Biden was licking his lips a tremendous amount -- it shows genuine emotion," Hartley said. "It's the human side of him and the animal side of him.
"When you see someone purse their lips, that's a typical male response to choke back emotion," he said. "It was good and genuine."
For those who plan to watch speaker after speaker take the podium, Hartley and other public speaking analysts said there are several cues one can look for when trying to determine the truthfulness of politicians.
Watch Charlie Gibson, Diane Sawyer and George Stephanopoulos at the Democratic National Convention TONIGHT at 10 p.m. ET on ABC.
As a general rule, Hartley encourages people who are unsure of a speaker to pay attention to the way his or her body moves, perhaps even more so than the words coming out of the speaker's mouth.
"Illustrators, or body movements, are indicators of what your brain is thinking," Hartley said. "It's your body punctuating your thoughts. A person should have synchronicity between the two."
There are few politicians, Hartley said, who are capable of keeping their pointer finger under wraps during a speaking engagement, despite the negative effect on an audience.
"Pointing makes people feel like you're accusing them of something," Hartley said. "It shows the person is trying to make you believe something."
Last night, Clinton managed to reel in his desire to point at the audience, Hartley said.
"He whipped people [in the air with his finger] at times, but then he remembered to change off and use the closed hand instead of the finger," he said.
Kevin Hogan, the author of "Psychology of Persuasion," said that people who point while they speak are often questioned by listeners.
"People who point when they're speaking -- I always put a big question mark after whatever they have just said," he said.
"Pointing has always been a cloak of true feelings -- sometimes it's lying or trying to look intense when you're really not," Hogan said. "It's never accepted well."
Patti Wood, a public speaking expert who has analyzed speakers for more than 25 years, warns viewers that political conventions are notorious for being some of the hardest-speaking engagements to analyze because of the charismatic nature of those who headline the events.