I used the WDW Tools Watch to get a reservation for Ohana for an incredibly specific time during my last trip and was able to snag a res after I was alerted of an opening a week before my trip. It looks like the 'Watch' program is no more which I'm assuming may have been Disney's doing. It wasn't a free service but a useful one. The only thing to do now is to be persistent and check for openings periodically as everyone else has said.