Our eyes may deceive us. Two witnesses of the same event rarely, relate tell the same story. On a smaller scale, we often misread words. If two words have a similar spelling, we may read the one that we think should go into a sentence rather than the one that is actually there. Our ears may deceive us. Research has shown that when people listen to a recording in which an occasional syllable is replaced by white noise, they think that they have heard the word they expected to hear. Most people do not even recall that part of the word was replaced with non-phonemic sound. 
However, most troubling if that other people deceive us and often we do not catch on to their lies. Despite believing that we can discern when people are lying, most people are not very accurate at this. The typical signs that we look for–eyes shifting, indirect eye contact, fidgeting or a stammer–may simply be evidence of nervousness. The more frequently a person lies, the better they are at looking and sounding confident about what they are saying.
However, no matter how proficient a person becomes constructing a lie, it is still more work than telling the truth. Typically while the mind is working harder, the body is less active. Often, the person who is lying may blink and fidget less than the person who is telling the truth. So you might look for such signs as a person pausing while speaking or appearing to think in between sentences.  But then pausing for emphasis is what good speakers are supposed to do.
On the other hand, you might just want to actually listen to the words people say. For example a person who uses “I” more often is more likely to be speaking from experience, and less likely to be intentionally lying. People that are not telling the truth use “we” or no first person noun at all. The equivocator is not likely to respond directly to a question, such as “Did you take my book from the desk?” with a simple “I did not take your book.” This person might respond with “We have not been near your desk.” A person who refers to “they” rather than naming specific names is more likely to conceal what actually occurred.
Negative people use negative words, right? Words like “but,” “no,” “none,” and “never.” Actually people who are more honest use these words much more frequently. People who are unwilling to answer a questions directly with a negation might be attempting to deceive you. Ask an experience equivocator and book thief about stealing your book and the initial response may be “There was a book on your desk?’’ or “What would I do with your book?”
So what do you do if you suspect that someone is lying to you? Looking directly in their eyes really won’t help. You have to make them work harder to keep up the lie. Continue to ask for more specific information on events, or question the person on events out of order. The person who created the fiction must now keep up with the details. However, you, too, have to keep up with the details to identify the contradictions. Remember that exhibition of nervousness under this kind of interrogation is not an admission of lying. You must not be fooled by the calmness of someone who excels at lying.
 Cell Press. “Auditory illusion: How our brains can fill in the gaps to create continuous sound.” ScienceDaily. ScienceDaily, 27 November 2009. www.sciencedaily.com/releases/2009/11/091125134655.htm
 Robert Trivers. The Folly of Fools: The Logic of Deceit and Self-Deception in Human Life, 7 January, 2014) http://time.com/77940/detect-lying/
 Gareth Cook. The Secret Language Code: Psychologist James Pennebaker reveals the hidden meaning of pronouns, August 16, 2011http://www.scientificamerican.com/article/the-secret-language-code/