I found a study partner, a co-worker, and that was key for me. We purchased the same book to study though we each had other books we referred to. We assigned ourselves a set of pages to read during the week and then on the weekend we met to do quizzes together and we looked up and discussed anything we didn't get right. I found a lot of free quizzes on the internet and we used review questions at the end of the books. It was not easy and I committed to almost a year of study like this, but it was why I believe I now am certified!
Had the years of experience. That is a key component in this. Then I got the CISSP Study Guide :
Certain there is a newer one now. Then studied for a month and took the exam 🙂
I had no idea what to expect. I feel that I did spend the right amount of time studying as I finished the 6-hour exam in about 3 hours.