Inconsistency. A liar won't be able to keep his story straight.

Nervousness. Someone who is blushing, blinking, and fiddling probably isn't telling the truth.

Hyperbolic. A liar will throw around superlatives. For example, "It's absolutely outrageous that you're accusing me!"

Stalling. A liar might ask you to repeat yourself before giving an answer, or will pause before speaking.

Avoiding. If a person tries to change the subject, or shuts down the conversation immediately, they might be lying.

Insincerity. A liar will exaggerate his emotions when not being truthful.