Practice, practice, practice.
An author friend of mine, Karen Hoover, does Flash Friday every weekend. She puts up two or three words to use as prompts and you go to it. You can write your story any time between Friday and Monday, but you only get one hour to write it. That hour includes the editing, and the story can only be a thousand words. (or less) She puts them all up on her blog and everyone votes on which they like best. No one knows which story belongs to which writer and you can't vote for yourself. (Yeah, I know what you're thinking!)
How fun does that sound? Way fun! It keeps your mind limber. So often we get stuck in ruts of only being able to write one way, or in one genre, or in one style. This little competition among friends has helped me do what I call sprinting. It's quick and entertaining. If you want to join in the fun, just let Karen know. The more the merrier!
Just be sure to vote for me. My story will be the best one. I'm sure you'll recognize it!