I feel thinking from another persons perspective is the greatest thing to do to get to know anyone. Just try and get into their shoes and live the way they do. Trust me, it truly works like magic. The person I wrote about was coincidentally my best friend, so I knew her pretty well, but when it came down to thinking like her, it wasn't all that easy. The trick is you must identify the some characteristics of that person, and dwell around those. For instance, I know she hates the sun, so it was pretty obvious that she would curse the sun in her head. Thats simply how I wrote my story, entirely from her perspective.
However, there were many things I felt were common, things like some descriptions and reactions. I didn't feel the need to change these things. Moreover, I stumbled upon a few similarities, I never knew me and my best friend had in common. Its very strange but true, that sometimes a person you believe to know really well, has a totally different side, which you would have never discovered.