I recently did a presentation at a local high school about the various aspects of writing and querying. One of the lessons I taught was on how to make your characters react, perceive, and interact consistently (or inconsistently, if that be the case) with the world around them.
To get a better idea or even just for fun, try this:
1- Find a personality test, such as the Meyer-Briggs test
2- Take the test as yourself (so you can separate yourself from your character)
3- Take the test as your character
Any test can work, but I love the Meyer-Briggs test because it tells you whether you are an introvert vs extrovert, a sensor vs intuitor, a thinker vs feeler, and a judger vs perceiver. Just knowing these things can really help you find out how your character makes decisions and how they view the world around them.
Try it out, and let me know how it goes! Lots of sites allow you to take it/them for free! (You just might learn something about yourself in the process, too.)
(P.S. There are also a ton of free personality tests on psychologytoday.com)
Bleeding Ink, Inc 
I never considered this! I think I might have to for both antagonist and MC for my WIP. Thanks!
Not to pimp my own ish, but in the side column on my blog I have a link to a free, very accurate MBTI that you can take in about ten minutes. Sorry, I don’t remember the link and can’t access at the moment. Love this idea, Rae!