The exam room in Canberra was hot and uncomfortable. 250 questions under such conditions was as much a physical challenge as it was mental. A big bottle of water was essential. During the exam, I found the best way (for me) to tackle it was a combination approach. The pass mark is 70%. I figured that I would be able to answer 50% with near certainty. That leaves 20% to find in the remaining questions. So I whizzed through one-pass, reading all questions, and marked on the answer sheet, only those that I was certain in my mind to get right. The remaining questions, I marked on the question sheet with comments. I put one symbol to indicate that I would be able to answer the question with a lot more thinking-time, and a different symbol for those that looked impossible. Then on the second pass, after a break, I tackled the ones that were a bit tricky. It helped to underline key words, and keep reminding myself that the "BEST" answer was sought, not necessarily the book-answer. In these cases, a process of ellimination was helpful. Cross off those answers that are certainly not right. Then keep reading and thinking until you either see the answer for sure, or are left with at most two choices. If left with two choices, then mark the question for another go at it next pass. If you come to the conclusion that no amout of thinking will make you choose one over the other, then go with intuition, (not a guess - use the right side of the brain!) Then have a break and something to eat. By this time, the blood-sugar level will need a boost. On the final pass, take your time over each question until you come to a conclusion. I found that questions that were in the "impossible" category at fist sight often went into the "i am sure of" category after a break, more thinking, and something to eat.
Harris's "all you can eat" book

was an ok read. But for me a tad verbose. I enjoyed the Krutz and Vines CISSP prep guide and wished that I'd actually bought the advanced prep guide. I really needed to do more prep on buisiness continuity and penetration testing, but with books specific to those topics rather than what you find in all-in-one CISSP texts.
My reading list was:
CISSP certification (Harris)
CISSP prep guide (Krutz Vines) [ Good - concise ]
CISSP for dummies (Miller Gregory) [ Good book! ]
Maximum Security (Anonymous)
Maximum Linux Security (Anonymous)
Hacking Exposed (Scambray McClure Kurtz)
Hacker Attack (Mansfield)
Complete Hacker's Handbook (DR-K)
Network and Internet Security (Auhja)
Internet Secuity Protocols (Black)
Secrets and Lies (Schneier) [ MUST READ ]
The code book (Singh) [ MUST READ ]
The RSA Press books on IPsec and others ( optional read )
Project Management (Kerzner) [ For reference - read parts of ]
Then, anything that I could get in the form of white-papers off the Internet, and texts written by Universities and Companies that showed up when typing in keywords and acronyms from the CISSP study guide available from ISC2.
I don't think any of the practice questions were representative of the exam. The ones in the exam ranged from dead-easy and obvious to "what the hell are they talking about?".
None of the questions in the actual exam seemed to demand a great depth of knowledge, but the range of required knowledge accross multiple diciplines, and the range of difficulty of the questions in the exam was very great.
So your study plan should be broad and wide, not too deep, unless you need to get to the details in order to form concepts. Some of the questions, might be based on industry opinion rather than hard facts, and these are the ones that give the most sweat during the exam, but reading undustry white-papers, and comments in forums from other professionals should fill some of this need.