The Wall Street Journal points out that when people are lying about something, they would usually unconsciously try to distance themselves from the situation. They tend to use the word "I" a lot less.

You can see this trend quite often in high powered people and bosses, which makes you wonder if using the word "I" is actually any indicator of hiding the truth. But still, as WSJ explains:
Researchers analyzed the language on Twitter of Boston bombing suspect Dzhokhar Tsarnaev. Mr. Tsarnaev used "I" words (I, me, my, I'll, I'm, etc.) less and less in his tweets as he got closer to the bombing, according to not-yet-published research by Brittany Norman at Midwestern State University in Wichita Falls, Texas, and Dr. Pennebaker.

The researchers analyzed all 856 of Mr. Tsarnaev's original tweets between October 2011 and April 15, 2013, the day of the bombing. They found that Mr. Tsarnaev's use of "I" words dropped significantly as the bombing approached, with the biggest drop appearing in October 2012 (to 4.81% of his words from 9.57% the month before).

"The data suggest that Mr. Tsarnaev made the decision to do something that he had to hide at that time," Ms. Norman says.
While that isn't a definitive way to spot a liar, it is something you can add on to your spot-a-lie skillset.

[The Wall Street Journal]