The best way to get a handle on the difficult question of spotting a lie is with your unconscious mind. Look at the whole face and torso, and ask yourself, Sincere or insincere? Then let your subconscious go to work. It’s very good at picking up whether the whole picture adds up to a consistent expression. For example, is the mouth set in a smile but the eyes are cold?  Insincere. Are the eyes fixed on you with beguiling stillness but the hands are nervously intertwining?  Insincere.

The next most important place to look after the face is the orientation of the head. Most of us, when we lie, turn our head away or tip it up or down so as to move it away from the other person. That's why you don’t want to focus too much on specific gestures, but rather let your unconscious mind pick up on the general situation.  If you look too much at the eyes, for example, you may miss the fact that the head is turned down and to one side. So again, ask yourself, Is this person sincere or insincere? And then take in the whole person. You’ll be able to tell most of the time.

Generally you’ll be able to pick up on the attitude of the other person right away, especially if it’s a loved one or someone you know well. I had a cancer scare a while back, a condition that turned out fortunately to be benign, but the morning that I came back from the doctor, my wife instantly asked me when I walked in the door, “What’s the matter?” She knew something was wrong because my whole body radiated concern.

So look for that overall feeling you get when you pose the question to your unconscious mind.  It's the most reliable way to tell. 

For those of you who are detail-oriented, you'll want to know some of the specific 'tells' anyway.  Beyond the eyes and face, look for the torso to be turned away (lying) or toward you (truth).  See if there are defensive gestures from the hands and arms and signs of agitation from the hands and fingers. And look for contradictory behavior from the legs and feet. If your spouse says, “No, everything’s fine,” but his feet are oriented strangely or his legs are awkwardly crossed away from you, those are signs to check into his story further.

Also listen for signs of strain in the voice. If the voice is carefully controlled or a little higher pitched than usual, the person may be attempting to conceal something.  The world’s best expert on lying, Paul Ekman, has found that people who are lying slow down (in an effort to control) their voice and even their facial gestures and other mannerisms. But ordinary people can also rush to get through an awkward-feeling moment. So the main thing to look for is variation from the norm, which you should know well. 

Spotting a liar in a group of strangers is a completely different exercise.  Ekman has made a career out of detecting micro-expressions that signal concealed underlying emotions.  But it's an imprecise science (unlike on the fun but inaccurate TV show, 'Lie to Me') because without much more detail, you don't know why the person is concealing the emotion.  Is it fear?  Rage?  Excitement?  To understand that, you have to get to know the person better, and that takes time.