First look at some web pages with BASIC information just to have some feeling! Try this one for example:
http://trailblazer.demo.jboss.com/EJB3Trail/ You'll have some feelings and you'll see something that also WORKS in practice.
Then, start with this book: "Pro EJB3 Java Persistence API"
Read this one carefully, make notes. This is a VERY GOOD book. It won't cover everything for the exam, but start with this one! It will help your understanding a lot!
After this one I would go for "OReilly Enterprise JavaBeans 3.0 5th Edition". At this level
you should write also your own EJBs, Interceptors etc.
After this, use Mikalai Zaikin's study guide (
http://java.boot.by/scbcd5-guide/ ) to cover the rest what is missing from the books above! Of course, search engines are also your friends!
At least, this is the plan I follow.
Good luck!
Andor