The truth is everybody does it from time to time. People dial telephone numbers and they get a wrong number only to find that they've read the last two digits backwards. Everybody does it, but dyslexics have this tendency to a higher degree.
For 'King Cole's American Salvage,' I rode around in the wrecker with a local driver and watched him deal with customers and hook up the cars. I watched the guy who tore apart the cars in the junkyard. I also wrote poems about those guys. I loved hanging around the yard.
But things such as 'Harry Potter', all I can do is shape my character, seek the director's approval on that, and basically take it from there. Professor Flitwick in 'Harry Potter', I kind of defined how I saw him from reading the book, and luckily that matched up with the director's vision.