I use the Clover Flat Flower Head pins. They are nice and long and firm but slide easily into multiple layers. I get mine at Joann's or Hancocks with a coupon of course (or when the notion wall is 50% off!)
http://www.joann.com/dritz-flat-flow...kg/xprd315862/ I pin from the outside edge inward.
I only pin when sewing the front of my binding to my quilt sandwich. After that, I use the Clover Binding Clips to hold the back of the binding in place when sewing either by machine or by hand. Amazon has the best price for these lately
http://www.amazon.com/Clover-Wonder-.../dp/B004ZKPX8A