Ever see Whitey Ford pitch? He had the greatest pickoff move in the major leagues. Andy Pettitte wasn't any slouch either.
One thing a pitcher has to watch out for is that he doesn't spend so much time and effort trying to pick a runner off first that he loses focus on getting the batter out. There have been so many instances of a pitcher throwing over to first and throwing over to first and throwing over to first because he's afraid the batter's going to steal on him that he loses his concentration, and when he finally delivers one to the plate the batter loses it in the upper deck. My pitching coach once told me that you could throw over to first once, maybe twice, just to let the runner know you know he's there---and go after the batter, because he's the one you have to get out!
I remember a funny story that illustrates a good pickoff move. The Giants, when they were in New York---oh, this was back in the '30s---once had a guy on first base who was picked off. When he returned to the dugout the manager started in on him, and the player said that he had been standing there at first base tapping the bag with his toe---and the pitcher got him between taps.
Timing is everything here.