(Must do) Familiarize yourself with SCJP/OCPJP 7 Upgrade exam process and topics. The best place to get information about it is Oracle Certification Website. or else you can also talk to our team members
(Must do) Whether you are at the early stage in your preparation or you have written 100s of 1000s of lines of Java code already, it is mandatory that you take a book relevant for this certification. We recommend OCA/OCP Java SE 7 Programmer I & II Study Guide (Exams 1Z0-803 & 1Z0-804) Oracle Certified Professional Java SE 7 Programmer Exams 1Z0-804 and 1Z0-805: A Comprehensive OCPJP 7 Certification Guide
(Must do) Other than a book, you would also need to appear in a reasonable number of practice tests. That will help you to assess your topic-wise preparation level and concentrate your preparation on weak areas. It will also expose you to a variety of OCPJP certification exam questions and set the right expectations. In case you want to take a look at some of the sample questions you can try OCPJP 7 Upgrade Exam Sample Practice Questions
(Optional) Register in a good SCJP/OCPJP 7 forum to post questions and discuss certification exam preparation related queries. This will be helpful for your study. One such forum is Coderanch.

“By failing to prepare, you are preparing to fail.”

Benjamin Franklin

Start your preparation today by checking your current level of understanding, appear in free SCJP/OCPJP practice questions.