Write down ideas, all the time. Keep a little notebook handy (Nabokov carried around index cards) and write down ideas for stories or articles or novels or characters. Write down snippets of conversation that you hear. Write down plot twists and visual details and fragments of song lyrics or poems that move you. Having these ideas written down helps, because they can inspire you or actually go directly into your writing. I like to keep a list of post ideas for my blog, and I continually add to it.