Is simple, take a personality test. Actually, take several personality tests as each one asks slightly different questions. I specifically am recommending that you take tests that align with the Jung and Myers typology as I believe people, in general, are sliding scales not neat little packages. I also recommend you read the accompanying information on each of the websites as well as spending some time researching the different personality types to gain an understanding of yourself as well as others.
Basically, though the Jung-Myers topology consists of sixteen basic personality types, based on combinations of the following four areas.
general attitude:
Extraverted (E) vs. Introverted (I)
Function of perception:
Sensing (S) vs. Intuition (N)
Function of judgement:
Thinking (T) vs. Feeling (F)
Balance of Perception and Judgement
Judging (J) vs. Perceiving (P)
Now, do not be surprised if you discover that you do not cleanly fit into just a single personality type. I myself am borderline on Function and Balance to such a degree that I fluctuate between INTJ, INFJ, INTP, and INFP usually within 1-3% on any given test. So go and take the following tests and maybe gain a bit of insight into yourself and others.
http://www.humanmetrics.com/cgi-win/jtypes2.asp
https://www.16personalities.com/free-personality-test
http://personality-testing.info/tests/OEJTS/
http://similarminds.com/jung_word_pair.html
and for fun try this one as well
http://www.testcolor.com/personalitytest/personalitytest.php