Here are some tips professional interrogators use to get the truth out of the bad guys (apart from physically beating them up) – all of which are completely applicable in everyday situations as well:

Carefully listen to what the individual is saying and look for discrepencies

Watch for eye contact. Lack of it indicates something fishy. Good liars of course get over this easily.

Read their body language. Figgeting, touching thier face, scratching, wiping or touching their chin often indicates lying.

Look at eye movement. People looking up and right are telling the truth while up and left is usually a lie.

Ask one question where the person does not need to lie and one which requires the person to answer with some imagination. Notice the eye movement – the one in the second case will repeat if they lie later.