Remember, there is no 'one size fits all' when it comes to body language. If you are really interested in being able to read a person's body language accurately, you may have to 'study' that person for some time. What is true for one person may not always be true for another. For example, when lying, some people break eye contact, while others ensure to maintain even more eye contact than usual so that they won't be suspected of lying.
Typically, the most unique body language can be found in nervous habits. While there are lots of actions that most people perform when nervous (such as shifting weight or darting eyes), there are other actions that could be based off of someone's past or just something they're insecure about. For example, someone might brush or trace a noticeable scar with their finger when nervous.