Just as in bluffing while gambling everyone has their own distinct "tell sign" physical reaction, kind of behavior, or habit that gives (or tells) others something isn't quite right.
Unfortunately (you have to spend time and study a person) to learn what (theirs) are. Some people give you a (rapid answer) and change the topic immediately. others (never answer the question directly) or give a long rambling answer, some folks blow up in anger first in hopes of intimidating you and then they drop an answer on you with the belief you won't dare ask a "follow up" question.
There are those that avoid looking you in the eye, others make you repeat the question or ask for clarification to stall in order to come up with something which may also include answering a question with a question. Some people find it hard not to smile when they lie!
The best liars always sprinkle in bits of the truth and have mastered lying by omission. The art of lying without lying.
They simply allow you to assume. This allows them deniability.
"I never (said) that!"