The first step is well, ACTUALLY GET A BAD REVIEW.
Realize NCNS, even if they say "Review" in the title, don't get attached to your provider profile. I.E. guys browsing through providers won't see a negative review.
Only those who look more closely will see anything.
Do your best to make that anything, if it is negative, be as unoticeable as possible. Engaging in long drawn out threads will only serve to highlight a negative thing and make it more visible.
So if a guy does do more research and sees one ncns and nothing else, chances are he looks over it. However, if he seens a 6 page thread, he may decide to move on and pass up possible drama.
If the NCNS is truly a one off circumstance, it will get buried will all the good.