If you're telling the truth, it's best to talk about yourself, make limited eye contact, and keep your hands relatively still.
According to a recent study from the University of Michigan, those behaviors are more particular to truthtellers than to liars.
The researchers, led by computer scientist Rada Mihalcea, looked at 118 video clips of public court trials assembled by the Innocence Project, a non-profit that tries to reverse guilty decisions.
Mihalcea and her team cross-checked those videos with people giving their opinions on movies that didn't exist. Together, the evidence put together a pretty robust picture of lying.
Some of the biggest tells included wild hand motions, heavy eye contact, saying "um" and referring to "he" or "she" instead of "I" or "we," head nodding, and scowling.