I passed the OCPWCD 5 exam a day before yesterday with 89% marks. This is the fifth certification I added to my resume (SCJP 1.4/1.5, Zend Certified Engineer for PHP 5, OCPWCD 5, MySQL 5 Certified Associate and a Python certificate exam that's offered by Oreilly)
To be frank, 89% is quite a decent score I think since I'm not from the Java realm and I haven't worked with ANY of the Java technologies since late 2007.
Here are a few tips that I recommend to prospective candidates.
1) I studied two books diligently - the Head First Servlets and JSP and a book (I do not remember it's title ) by David Bridgewater.
2) I did have a problem in memorizing the APIs (and mind you if you to pass this exam, you SHOULD memorize the APIs) so I had sketched out a large class diagram of the APIs on a chart and framed it in my study room and used to go through it early in the morning and late at night before bed.
3) I programmed like HELL. Rote Learning is not important, you should understand. I recommend to not go for J2EE IDEs (Eclipse) while doing sample assignments. I used Notepad++. Do write code as much as you can.
4) Chalk out a strategy plan and abide by it. Plan your study schedule.
5) Lastly, stick to the Head First Servlets and JSP book, this is your bible for the exam.