Some people prefer it the other way round. They do not want to read or hear about the story at all. They think that will spoil it when they watch the movie. The exciting parts are not exciting if they know what's going to happen.
Recently, I went to watch The Da Vinci Code. I did not managed to read the book first. There's a lot of things that I do not catch. How they solve the puzzles, etc. I did managed to catch the gist of it though. After that, I managed to get my hands on the story and is reading it now. Now I am able to understand those that baffled me in the movie. However, I realise 1 thing. The exciting parts are not exciting as I know what's going to happen. :P
I think I still prefer story 1st, then movie.