I would like to thank Frits for preparing some amazing notes! Those notes are the second mostly used source by me (first was EJB specs )
Apart from specs and Frits' notes, I studied EJB 3.1 book by Rubinger and Burke. It is a good start for this exam. Another book I used was EJB 3.1 Cookbook by Reese. This book is full with code snippets (the name itself says it all) and this too, helped me to gain some more knowledge.
And last but not least - Enthuware. Solving those questions not only gave me idea about overall exam pattern, but since (some of)those questions are quite off-bit, those really helped me to understand small (but critical) pitfalls.
Overall, I feel this exam is not that 'tricky'. I was worried about the time(110 minutes for 60 questions), but after I practiced Enthuware questions, in real exam I had enough time to make a second pass for all questions.
I would make few suggestions:
1) If you don't have any exposure towards EJB development, do not go to EJB specs directly. In such case, I would suggest Rubinger & Burke for theory and Reese for practice (you may skip JPA and Entity Beans sections if you are only focusing on certification).
2) Once you are comfortable with coding, then you can go for specs.
3) Real exam questions are based on specs, so make sure you understand specs thoroughly (I made around 3 passes over the specs). You may skip sections dealing with EJB 2.x and 1.x.
4) Go through Enthuware practice exams. This will give you idea about your strong/weak areas.
5) For reference, refer the specs; for quick revision, refer Frits' notes. Ivan's notes are also very good(though lengthy, those are definitely worth at least a single reading).
6) Don't panic. You are not supposed to memorize each and every class methods, or each and every tag in DD. However, you must be aware of important classes, methods (especially what is 'not' allowed/possible).