Help with analyzing characters?

I love to write. But I'm a little...common sense deficient. I can't read people very well, therefore I'm not very good at analyzing characters. When I write, my characters come out so stereotyped that it really annoys me. I've been getting better at it (my lit teacher this year is better than previous ones, and reading for symbolism and character traits has become a little easier), but I'm still not great at it. Like with Romeo and Juliet, it took me a while to realize that Romeo was impulsive, and that was his tragic flaw. I mean, I knew this, somewhere in the back of my mind, but I just never acknowledged it. I know you're probably thinking I should give up my dreams of writing, but I have my own personal reasons for sticking with it. Anyone know how to help me? I know it's a tough question, but any tips would be great!