Jay,
As a caddy myself, the most important thing a caddy can do is develop a good relationship with the player. Even if the caddy stays quiet, learning quickly what the player wants out of the caddy is important. Sometimes I caddy for people who prefer to interact with the group, and thus I hardly end up saying a word the entire round. I stay quiet until I know for sure it is ok with my player to put in a word.
Most of the time I dont read greens for players - I never even try to unless asked. There doesn't seem to be a worse thing to do then suggest a club or read a green for a player that doesn't want it. However, I am more then willing to offer suggestions to my player when asked.
The truth is, at least for me, caddying is a lot different when at a public course versus a private club. At a public course, players are generally a lot more outgoing, and ask for advice a lot more. I always think this is because at a club, the member has played the course plenty of times enough to know how greens break, what clubs to hit, etc. As long as I can get quick feedback out of the player for what he expects out of me for the round, I accomodate those needs to the best of my ability.
Hope this helps.
Cheers,
Jordan