AVCA Video Tip of the Week: Chair Drill to Improve Setting Technique 

Three

How many fingers to use is more a question of style, rather than technique. If you watch professional setters, some set with three fingers, some set with five. I think the point here is to find what works for you best because we all have some wrist and finger mechanics differences. There are more important things to focus on, such as high contact with the ball, work of legs, training the side view for the setter to see the block, etc.