Say you have four hours where you have absolutely nothing to do. If you're anything like me, this sounds joyous until you are actually faced with what to do in those four hours. It's something like the universe saying: "You have four hours of nothingness ahead of you. You have only a tablet and your fingers. Go!"
Luckily, I had just finished (as in, less than an hour ago) Natalie Goldberg's Writing Down the Bones, and I had plenty of new techniques in my head to put into practice. So I opened Memos and began typing. I'm not sure what you would call the piece that I produced. A short story, a scene, a memory from my character's past. I called it a free write. It was two paragraphs and little bit of dialogue. I did three more of them. Free writes, as it turns out, are as addictive as potato chips.
There aren't many rules to free writes. Step one, find something to write on and something to write with. Step two, start with any random sentence and don't let your fingers stop moving. Step three, you have five to ten minutes, preferably less. Step four, stop when the piece feels done, or whenever you feel like stopping. Then do another.
They're not supposed to be good. They can be typo-ridden messes, filled with punctuation mistakes and misspelled words. They're practice. A childhood memory, a seemingly unimportant observation, a fight, a character's stream of consciousness. They're ways to tune voice, explain things more clearly, maybe to try out a new technique. But they're pretty darn useful when you're bored out of your mind.