I was pleasantly surprised to pass the SCWCD 5 exam with a score of 92%! For anyone who may ask, I strongly believe that this test is not as difficult as the SCJP exam. I should note, however, that there are a few topics of the SCJP 5 exam - specifically autoboxing and unboxing - that may show up on the SCWCD exam. I wanted to share my thoughts on exam preparation.
1. HSFJ - This is the ultimate book for this exam. I used the First Edition that doesn't cover SCWCD 5, but it is more than sufficient for preparing for the test. (See others posts on this topic.) I read it twice and did the practice questions at the end of each chapter. You should really do these. The authors do not give you the number of answers for the questions so they are more difficult than the problems you will discover on the exam.
2. SCWCD Study Companion by Charles Lyons - HSFJ is a great book to get you up to speed on the exam, but I also found it helpful to have Charles Lyons' book handy too. For the practice questions you may get stuck on from HSFJ or to fill in specific details about knowledge gaps you have, this is a great reference book. His questions are much more challenging than those in HSFJ and quite useful. I did not, however, try his full length practice exam.
3. Enthuware JWebPlus - This is truly the best practice exam software out there. You get more than eight exams, and they all were quite challenging. The explanations of the answers for each question were extremely helpful. And the software only costs $29.99, so who can beat that? I'd advise, however, against buying the Whizlabs software. I ran through the five practice exams and found numerous errors. The software marked questions wrong for which I truly had the right answer. It was frustrating.
4. Sun Practice Exams - You can purchase two practice exams (60 questions each) from Sun for $55. You should ABSOLUTELY buy these. I ran through them the night before the exam and score decently well. They really give you the best idea of what the questions will be like on the actual exam and seem to hit a fairly equal distribution of all topics. I HIGHLY recommend these ones.
I hope these tips help out. I did not score as high as 92% on any of the practice exams I took. I found the practice exams all to be more challenging than the actual exam, but I believe they were great practice for learning the material, especially if you read the correct answer explanations.