An excellent, short article about What Happened to Experimental Writing? by Susan Steinberg. She astutely observes the importance of process. And while rules are generally ridiculous for experimental writing, I think she does a good job of applying three in her own writing:
“Experimental writing a) had to be inventive or had to bend or advance or subvert preexisting approaches to writing, b) had to seriously take into account the possibilities of form and/or structure and/or syntax and/or language, and not just content, and c) could not just look different on the page.”
Rules to consider. I particularly enjoy negative rule c. Often people mistake visual disparity with traditional paragraph form with experimentation. But the middle rule is perhaps the most important: form, structure, syntax and language as focus. I love the flash form (prose poetry/flash fiction) because of the flexibility the brevity offers to play with these things.