You will need a combination of things here:
1) Personal hands on experience with the product. You can work with sample applications (WebLogic download is free form the BEA web site).
2) Theoretical knowledge (books, online study guide, etc). I would recommend reading my preparation article for some pointers: http://www.whizlabs.com/articles/weblogic-article.html
3) Understand, practice and validate your knowledge against the kind of questions the actual exam will throw at you.
This is where the Whizlabs simulator plays an important role. The simulator provides a huge set of questions based on the kind of questions asked in the actual exam. It provides explanations on correct and well as incorrect answers, which is by itself a good learning experience. With whizlabs past record, working with the simulator will highly increase chances of (if not ensure) success in the exam.