That's when I started paying attention to writers like John Updike, who used vocabulary that I was already familiar with, but in combinations or places that were unexpected. I came up with much more creative lines in my own work, like this example to describe part of a scene where a character was rummaging around his apartment after accidentally cutting off two of his fingers: "He left bird prints on the walls."
I think the key to improving your language in writing is to be able to recall more of the words you already know--your active vocabulary. I try to do this throughout the day, challenging myself to come with quirky or interesting ways to speak with other people. You'll be surprised at how fun this is! I'd say about once a week I get someone to smile simply by using an adjective that was a little unusual. It loosens me up so that when I get to my writing, I'm able to come up with a larger variety of words without having to look anything up.
How do you improve your writing language? Do you have any great lines that show off your language?