This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
I think you should know things like what is in the root of a collection heirarchy. Maybe what interfaces are implemented by Maps , Sets , Lists they are straight forward. Things like what collection can hold unque values. I've seen questions on a mack exam like can they hold primitive values ? Answer no they deal with objects. So read about stuff like that. I find collections very easy topic.