I go for long walks when I feel like I have a block in my writing. I also try to write something everyday. I know it seems a bit off to talk about writing when one has writer's block, but I was reading an interview with George R. R. Martin and his suggestion for up and coming writers was to write something everyday, no matter what it is. Being able to write is like exercising a muscle and sometimes it gets strained. Therefore, if you work it out on a regular basis you should be able to have shorter bouts of writer's block. You might even be able to clear out enough fog to eliminate writer's block altogether.