The best thing to do with writer's block is to completely ignore it, and just keep writing. The best definition of the so-called malady that I've ever heard is that writer's block is simply a failure of nerve. I have found this to be perfectly true. You've simply got to keep believing in yourself and your ability to tell a compelling story, and keep putting words on the page. Eventually, even after the darkest of times, things will start to make sense, and a story will emerge. Writing is a profession as much as it is an art and a skill, and the more the practitioner treats it as a job, the less stress s/he will have to endure. After all, we don't hear too much about "plumber's block," do we? We go out every day and we simply do our job, which is to keep writing.

I'm not sure of what you mean by a writing prompt, but if I need something to get me going on any particular day, I usually start with something like answering an email such as this one, or writing down a recipe or a joke. Believe me, getting a joke to read funny is an excellent warm up. When I'm actually in the midst of a story or book, usually all I need is a quick re-read of what has come before, after which I try to write a scene that's different from the last one in tone and setting—e.g. indoors vs. outdoors; description vs. dialogue. This tends to keep things fresh and moving.

The best advice I had as a young writer was really a blanket criticism that a creative writing instructor at UC Berkeley, Jackson Burgess, gave to my small class of fifteen or so hopeful writers. He announced about midway through the course that only one of us had a chance of becoming a professional writer, and then he told us who it was—and it was not me. "Oh yeah?" I thought. "Watch this?" I immediately sat down and started my first full-length work, which did not get published, but which taught me many lesson and set me on the road.