Thank you Venkata.
What I did was read K&B book twice. On the first read, I just tried to understand the concepts being taught. It's impossible to remember everything so I just tried to understand what I was reading. On the second read, I made my own notes on the important concepts, chapter-by-chapter. I made about a little over a hundred pages of my own notes on letter-size bondpapers. So by this time whenever I needed to review, I just consulted my notes and re-read it over and over when time permits. Answer all the exercises that come with the book and review it from time-to-time.
As for the mock exams, the free ones are already enough to pass OCPJP exam.
ExamLab is a must. I also did CertPal. It can get discouraging when you get low scores in ExamLab but it's normal. I find the mock exams harder than the actual exam. Just do your best in them and
you should be good for the real one.