I usually putt the best when I set up with the TOE of the putter UP in the air a little, similar to the way Ballesteros used to set up. I've tried flatter putters where the club sits flat, but don't get good results. I've noticed that many players do this to some extent.
Any ideas on why some players tend to go to this setup? I have used Ping Ansers and Pals when this works the best. One theory is that this gives the putter a litle "trap"... like a hockey stick.