Sharing my experience of passing PMP exam in my third attempt is no less than telling a life story. I always thought I was good at concept questions and exams. But had to go through it 3 times.

1st attempt: To start with, I was constantly guided by a PMP certified PM manager. He told me which books to go through and to attempt multiple quizzes before the actual test. I did that, well at least I thought I did.
In my first attempt, I went through Rita's PMP book twice and made a mistake of not reconciling much with the PMBOK guide (6th edition). I attempted very few quizzes, felt confident and went for the test.
As expected, I failed to clear the exam.

2nd attempt: I went through both the books again, did quite a lot of practice quizzes (mostly free quizzes available on the internet). Repeated the exams a lot of times, got happy with the result and felt knowledgeable
and confident. Went for the 2nd attempt within a month. Was DEVASTATED because i thought I had good command over the concepts. Failed again, with almost the same results as the first one. Did not manage to improve on my weak areas.

3rd attempt: I specifically focussed on my weak areas as identified by my two previous attempts. Went through the PMBOK guide, focussing on those weak areas. Still had some concepts that were not clear enough.
So I had Skype and phone meeting with my mentor. Picked out specific quiz questions I had problems with and tried to understand the logic behind the basic concepts. Practiced more and different kinds of
quizzes (free and paid). Out of these two different and new techniques, I feel discussing and arguing about my concepts helped me clear out my perspective more.

My Conclusion:
1) PMBOK guide is very dry, dull and boring but you CANNOT afford to skip/skim through it. To be able to know the terminologies of the exam, you have to go through each word of the PMBOK guide.
2) Books like Rita's PMP and others are much more easier to understand the concepts. In my opinion, Rita's PMP book is really easy to understand and should be read after you go through the PMBOK guide. Rtia's PMP book
also has small quizzes at the end of each chapter for quick concept check.
3) In my opinion, enrolling in the PMP prep courses is for each one to decide and also depends on the timeline you have for attempting the exam. You can do the prep alone, but it will be way more challenging than being in a group. But one thing is for sure; the more people you get involved with while preparing for the exam, the better your preparation is. Bouncing ideas/thoughts of different people helps you clear the concepts better than any book. If you do it alone, like me, with lesser discussions, you'll be less prepared than you think (my example to learn from).
4) Like me, if you are worried about the mathematics part (cost management/risk management), DON'T be. There are very few mathematical concepts and they're easy to understand and get a good grip on with some practice and guidance.
5) If you fail in an attempt, it is very important to recognize your weak areas through the detailed exam report the PMI provides. You need to work on your weak areas and not go through books/quizzes randomly. Focus specifically on your weak areas. Talk/discuss with someone to clear your weaker areas/concepts/chapters.
6) Try multiple/different kinds of quizzes. Unlike me, in my first two attempts, do NOT stick to one quiz (Rita's/Cornelius/etc.) Spend some money if you can, it's an investment which I learnt late. In my humble opinion, Rita's PMP simulator and Cornelius PMP prepcast are very good and give you similar, situation based questions like the original exam.

Hope this helps !