I'm doing some humor writing, and one thing that helps me come up with ideas is to try to visualize, as clearly as I can, the editor laughing.
This may seem to come perilously close to "The Secret" that I love to mock, but it's less about asking the Universe to buy me a new car than it is a way to cut through anxiety, to get around the inner critic that immediately says "That sucks!" to every idea. I think it works because the ideas are there, and they will start to flow (or at least sputter) if the anxiety/inner critic doesn't get too much in the way.
Other than that, coffee is very helpful.
