Train your observations skills by watching others (at a party for instance), writing your observations and your deductions based on these observations. Then find out all you can about the person or persons you observed, and take notes of what you find out. Lastly, compare your two notes and write an analysis of the differences and why you think these differences exist.
Use a notebook or maybe an app built just for that. Either way, there should be the following notes for each experiment: initial observations, deductions, facts after getting to know the subjects, analysis of the differences and the potential reasons for them.