Today I took OCPJP 6 and scored 96%. Thanks to javaranch, and all the ranchers. Thanks to Kathy and Bert for writing such a wonderful book, and practice exams.
I would love to share some of my experiences during preparation, and during actual exam:
1. The bible: Kathy Sierra & Bert Bates' SCJP Sun Certified Programmer for Java 6.
2. During my preparation I realized that if you want to dig deep into something Java Language Specification was certainly very helpful (although sometimes very hard to decipher!).
3. also try to read Java 6 Source Code which you can find here in your system, also read API Documentation, some of the Tutorials on Oracle's Site are really good, especially Regular Expressions and Collections tutorials are great.
4. and Javaranch. I know java far better now, than I used to when I wasn't here. Post your doubts, answer the questions, read the posts, and you will surely get a great learning experience.
5. practice as much as you can. Once you know the concepts, practice and experiment with code.
Mock Exams and practice questions:
I could not take enough mock exams (mainly due to my job, i guess). But I found the following practice exams very helpful, these exams prepare you for the hardest of all questions you can ever expect in real exam!
1. K&B Master Exams.
2. K&B Practice Exams.
My scores in these exams were around 70%.
During real exam:
Exam questions were very easy, as compared to K&B Master and Practice exams.
Some typos were there, which I really didn't expect.
Plenty of time: I answered all questions with 1 hour remaining and reviewed some marked questions in next half an hour and so ended the exam half an hour early, so you will get enough time to review your questions.