An aggressive drug-testing program would cut down on certain abuses, but its never going to catch everyone - or even close to everyone.
I do believe that in order to be a successful negotiator that as a diplomat, you have to be able to put yourself into the other person's shoes. Unless you can understand what is motivating them, you are never going to be able to figure out how to solve a particular problem.
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.

