If you are looking for specific restaurants then check out the touring plans reservation finder. I believe you can put in a couple requests and it will alert you if something opens. If it is a hard to get ARD you will need to jump on it right away. Otherwise stalking is your next best option and keeping an open mind for times - so maybe choosing lunch instead of dinner or dinner at 4 or 8pm because the prime 5-7pm is tougher to get.
I am not even sure if using a cancellation thread would be helpful as I even tried to coordinate a Ohana reservation that i was cancelling with another member of the boards -- I cancelled at a specific time and they still were not able to pick up my reservation.