How can we get better at spotting a lie?

Sometimes we are constantly being lied to by those people we date. Often times, we aren't very good at knowing when we are being lied to.
I see lying as the lowest form of cowardice. Usually, I can ascertain that it is happening. But some people are so proficient at lying that it becomes nearly undetectable.
To provide you with as much information as possible, I interviewed a number of people who are "experienced" at being lied to. They ranged from spouses who were cheated on, to landlords, policemen, and IRS agents. Here is a composite list of the characteristics they said to look for. The liar in question may:
* not be able to look you in the eyes. They will avoid eye contact and end it quickly if it accidentally occurs.
* exhibit irregular pauses when speaking. If they pause before speaking, they may be searching for the right words or answer. If they pause at the end, they may be watching your response to see if they successfully pulled off their scam.
* stutter, blink uncontrollably and laugh nervously after speaking.
* continually touch their face, mouth, nose or ears while talking.
* appear nervous or preoccupied. They fidget by tapping their feet, fingers or playing with their jewelry.
* have their exact story down pat. But when interrupted, be unable to resume from the point where they left off.
* contradict themselves. Their version of the truth changes over time.
* talk louder or with their hands to further emphasize their point.
* use the word "really" often. "Really, he/she is only a friend."
* act surprisingly nice, helpful or caring in order to mask their guilt.
One man clearly expressed his feelings when he declared that, "if it's a woman, and she is dating me, and she's talking, she is probably lying."