Once you have been writing for a while, you realize you can’t turn off that part of your brain. Every time I watch a tv show or movie or do anything that has a story line (even Dungeons and Dragons) I am very conscious about the decisions that had to be made.
What I mean by this is asking myself questions like “Why is this character there?” or “What if this character’s personality was different?”
I find that watching tv/movies or reading books allows me to improve my own writing abilities because I can pick up on decisions other authors have made that were successful. I also find myself paying attention to things that I see a lot and try to take a spin off of them (like my trio of characters poll I did a couple of posts ago). I noticed a lot of the time there are two girls and one guy (obviously not true for everything) and tried to change my trio to not be the norm as I saw it in my head.
Being a writer also helps you predict where the story will go, especially in mysteries. For example, watch an episode of the Scooby-Doo. If you have your writer turned on you will likely be able to pick out who did it the moment you are introduced to them. Similarly, I do this with my favorite tv show Psych. Basically you can show off your ability to figure things out sooner than your friends because you can understand the way it was written for the purpose of having that character who “did it.”