The things that trips up most first timers to Catalina is not being able to get a mooring at Avalon (often difficult without waiting some days) and then while waiting not being able to
anchor because they don't have enough
rode. The anchoring area by Avalon has a drop off. You need a long
rode in many anchoring places around Catalina.
Two Harbors is a nice place to moor but a little boring for some people.
There are a couple good books on the Channel Islands out there.
Boating and Diving Catalina Island by Bruce Wicklund comes to mind