If you have a player with a no-trade clause, what determines whether or not he will accept a trade?

I believe he'll accept a trade to a team that is a certain % better than you in the overall standings.  IIRC, I think it may be 3 spots better, so if you look at your spot in the waiver wire order, he'll accept a trade to any team that is 3 spots above you in the waiver wire order (which goes by overall record at that point in the season, or prior season's record if you're in the offseason I believe.)  So if your teams sucks, he'll be easy to move.  If you're team is good, it will limit the amount of teams that you can trade him to.