Review the certification requirements on the Oracle Certification website
For each exam, review the exam objectives on the Oracle Certification website
Perform a gap analysis of your knowledge/experience/skills versus the exam objectives (for each exam).
Create a study plan the that will help you close the gaps that you identified.
Utilize study methods that work for you. We suggest that these might include:
Practice – use the real product in a non-production environment
Training – take an Oracle University course or attend an OU seminar
Read – Oracle Press and many other publishers have exam and/or topic-related books available
Flash Cards – If you create flash cards with key points on them, you will learn both while you create them and while you review them
Practice Exams – look for available practice exams or sample questions