Tour caddies are a bit different from the "honor" caddies at your club. A tour caddy needs to be a sounding board, a researcher who understands stats, a psychologist, an encourager/motivator, and timely in his comments all at the same time. Did I mention enjoys travelling...
Steve Williams wrote a good book describing his philosophies and how he works with players. Check it out.
__________________
Golf can never be considered an enigma. ~HK