When you start off developing with CRM 2011 it can take you quite a while to understand how all the entities are related to each other.
So something which would have helped me is an Entity Relationship diagram and then now that I have a pretty good idea how it is all linked together I finally find one.
The good chaps at Microsoft have created one and you can download it here
The download contains a visio file for all the major areas in CRM. Actually looking at the list it seems a bit confusing