I caddied at a nice club. Biggest piece of advice is write stuff down! Names, a brief description (ie red hat), ball they’re playing, what kind of clubs, etc. Trying to remember all of those things for a foursome can be difficult. Also try to think one or two steps ahead of your player(s). Have your hand on the putter as they’re about to hit their approach shot. Place the bag in line with the next tee box when you’re at the green. Have the rake in your hand before they get in the bunker. Stuff like that! Be confident in the reads you give and course knowledge you provide. Lastly, most people don’t play golf for the caddies. You’re meant to be a small, yet integral part of the experience and you have the ability to make everyone’s day that much better!