Get a pen and paper.
Start writing about the first thing that comes to mind.
Stop after exactly one minute.
We were asked in class earlier today to do the same thing. I wrote about writing and came up with two sentences and a half. Others griped about not having enough time in an attempt to buy more thereof.
It was hard. Writing is hard. (You can’t imagine how much I am squeezing the words out right now.) But the exercise was harder because we didn’t have time to think. Or rather re-think. Up to this point I have edited the sentences above an average of three times.