I'm someone who works best with an outline for longer works, but have been writing short stories/flash pieces 'on the fly'. Keep in mind, these are very short stories, generally around 1000 words. Reading back on them, however, they're a very rough draft and maybe would have been better if I spent the time outlining or even doing a little character exploration first.

So, how do you write your short pieces? Do you outline first or just go with what's in your head?