When I was at Co-Lin, I had to take a English Lit class. Mrs. Crews my lit teacher made us keep a journal and at the beginning of every class she would make us open our journals and then she would just say "Go". We were just supposed to write. Our pencils weren't supposed to stop. If we couldn't think of anything to write then we were supposed to write exactly that. At the end of the time she would say "Stop", we could close our journals and she would start class. Oh this was a infuriating exercise for me. I would just get my brain awake and my creative juices flowing and then she would yell "STOP!" and start lecturing in her low, droning monotone voice. It was like letting me smell my morning coffee, but not letting me actually drink it!
However, I always did enjoy that little "brain exercise". Recently I have discovered a website that kind of lets me do the same thing. It is called One Word. Every day you go to the website and when you click go it gives you one word at the top of the page. It also gives you 60 seconds to type whatever pops into your mind about that one word.
Give it a try. It is almost as good as your morning cup of coffee!