That's a very good question, ennie. Personally I think insincere people tend to brag about their own qualities and they tend to show off a little; sincere people are usually quiet and their qualities come out over time. It's not always easy to see through people, though. I think it requires a lot of experience and observation. I think you'll get better at it with time. Wish you good luck! Let us know how it goes. Sending many hugs to you