Those who are interested in the upgrade exam (1Z0-810) though, should learn new features introduced in Java 8 to pass the exam. Here's a list of topics covered by exam:

As you see all of them are based on lambdas, streams and new Date/Time API. I find Java 8 Lambdas book by Richard Warburton very useful for these topics. It has all you need to know about lambdas and streams. As for the Date/Time API I think reading official documentation and having some practice is more than enough. Enthuware provides a mock exams for 1Z0-810 as well. 

If you are successful in your exam (and why you shouldn't be???) you will receive a printed version of certificate as well as its digital version, a plastic card and a badge:

Hope this will encourage you to get certified ;) 

To be continued...

Don't be afraid to fail a question in practice exams or those present after each book section. But if you fail one - read the explanations and make sure you understand why your answer was wrong.

If you feel that book is not enough for you - there's also official preparation tutorial from Oracle. Also don't forget that there are JavaDocs. You can learn a lot from them as well.

If you are not much of a reader but more of a listener then in that case there are also video tutorial for exam preparation. Check here for details. There's also a preparation course from Oracle as well.

Check JavaRanch Forum, if in your preparation process you stumble upon a question you'd like someone to help you with.

Practice, practice and practice

It's a good idea to practice, and write some code, while you are studying all those materials. It's much easier to learn and you'll be able to try all the things on your own rather than just believing what is written.

After going through all the topics (list of them can be found on corresponding exam page), you can do some mock tests. The book that I've mentioned comes with a set of mock exams, on which you can practice and determine your preparation level. Application has an intuitive UI and all the questions have explanations.

If you decided to go with a different book for studying, or for any other reason didn't get a CD with the book, do not get discouraged! There's even better mock exam and for very good price. I'm talking about the one from enthuware. It's only 10$ and that's a really good investment. This mock application has 500+ question. As far as I remember almost all of them are different from each other. Also UI is very-very similar to the one you'll see at the real exam.

You've studied hard and you are ready for the exam. But what should you do next? Well to be able to take an exam you need to purchase an exam voucher and register in test center for the exam. All of this can be done online. You can purchase a voucher either from Oracle or from Pearson VUE. You should check official information about the differences and choose the option most suitable for you.

Exam day has come

On the exam day you should come to the test center at least 15 minutes before the scheduled time to complete a few formalities. You'll need to sign a couple of papers and you IDs should be checked. If everything is fine you will be taken to exam room where your photo will be taken, you will be given a sheet of paper and you'll start your exam. Keep in mind that you are not allowed to have anything with you in exam room. If you'll be suspected of cheating - your exam will end :).

After you complete all the questions and submit your results, you'll receive a printed confirmation of you taking the exam. The actual results with the score will be available within 30 minutes after you submit the exam. Corresponding instructions will be emailed to you.

Certificate

After the exam and waiting for results it will take up to 48 hours for Oracle to provide you with downloadable version of a certificate, badge and links to OCA logos. When you receive the email that you were grunted a badge from Oracle there will be instructions on how to accept it. It looks nice: