As a fiction writer, I've never had writer's block. I went the painful process of discovering writer's block years ago when I was writing marketing. The steps I found which helped me overcome and avoid writer's block then have worked great for fiction writing.
Those steps are:
1. Tons of research. I do as much research as I can before I write a single word. 2. Create a basic outline. I don't script any little detail but I do list key points for each scene like where it takes place, the key people who are there (with the mental permission to add or change them if I need to), any clues or red herrings that need to worked in. 3. Scan my outline and pick a scene that sounds interesting. Everytime I've ever tried to write from start to end -- be it a term paper, marketing piece, or work of fiction, I eventually hit a spot (and it's never the same spot) where my brain locks up. By giving myself permission during the initial writing stage to skip around, writing becomes a lot less stressful. 4. "Don't think, just write." It doesn't have to be perfect when you first write it. You can refine and perfect it at a later time when you're editing. 5. Give yourself permission to let it rip. Just write anything that pops in your head. Even it doesn't make sense. One of my "let it rip" sessions gave me the idea on a better ending for "The Countdown" and what the next book would be about. 6. Write with music. Or not. Most of the time, I write with music. But sometimes as I scan my music collection, nothing looks good so I don't force it. I write in silence then.