I am a real proponent of Myers Briggs (MB) at the best of times, I have done the test twice, and come out with the same profile. When I first learnt about MB it kinda blew my mind. If you do the official test you get all kinds of information from it, like – how you react under stress, how others perceive you, and what your weaknesses are likely to be. I know I’ve said it, but it really did blow my mind! It was how others perceive me that had the greatest impact on me. My point – is that it got me thinking about how my characters might be seen by each other, or by the readers, or by anyone really other than me. The MB types kind of give you key personality types and I really like working out which types my characters are. Above should be a picture explaining the key characteristics of each type, and a quick google of Myers Briggs will give you countless websites where there are free tests – you could even do the test in character to give you their profile, and obviously google will give you lots of info about the types.
Let me know if you think this is helpful