1. Establish a baseline:
A base line is a regular behaviour of the given person (you suspect to be lying). When a person lies, he usually deviates greatly from his regular behaviour.
2. Make a conscious effort to keep track of their body language.
3. Look out for microexpressions:
4. Watch out for too detailed stories and answers, or if somebody tells you too much, i.e. excessive info, e.g. if you asked somebody how his room look like, and he tells you something along the lines of "my room is very beautiful and tidy, but the corridor connected to it isn't comfortably wide", it may be a sign that he's avoiding the main object of the question (his own room).
5. You need to notice person's eye movements.
Also, the precaution must be taken, since there is a popular belief that liars avoid the eye contact. The truth is liars can look you straight into eyes to seem more sincere.
When they tell the truth (remembers what they saw), they usually move their eyes to your right.
When they tell you a lie (think something up), they usually move their eyes to your left.
It can be reversed for left-hand people.
6. Sincere replies come relatively fast, while lies must be rethought to seem reasonable and consistent.
7. Change a subject to see if the person you talk to seem to be relieved or not. It can be an indication that he could have been lying and he's relieved that you stopped to question him / talk about the uncomfortable subject.
8. You can even shake a hand with a person suspected by you to be a liar, a fast goodbye handshake, in a quick attempt to ascertain if he was lying. The temperature of his hand can be colder.
* * *
Types of people (taking lying / telling the truth behaviour into consideration):
Illustrators: they 'illustrate' what they remember, and they frequently use their hands to talk.
Manipulators: the opposite of illustrators. They play with a wristwatch, jewelery, pull an earlobe, etc.
Also, before you recognise which are which, establish a baseline - it's necessary to know how they act normally.
FBI Agent Explains How To Spot Liars