I read the excellent book "SCJP Sun® Certified Programmer for Java™ 6 Study Guide" by Kathy Sierra, and Bert Bates in one week.
While reading, I opened Netbeans IDE and examined the sample code, trying out variations of the code.
So I had a long week, and long weekend: reading, programming, experimenting, learning...
Without that preparation I think I wouldn't manage to pass the exam!
After reading it I took some mock tests.
So I'm quite happy with the result.
Although I'm programming in java for about 10 years, reading the book I learned some new details about the Java language.