The first time I took the PMP exam, I used materials from the company I work for. They put me through the Velociteach course. I also took some practice tests from their material, and read a bit of the PMBOK Guide. I studied for months, but I failed the first time around. I realized that the questions I used to practice were nothing like the exam questions and there was some material/concepts I didn't even know about! I kind of figured I did poorly on the exam, I felt it throughout the whole 4 hours.
Things I did differently:
I found the PrepCast Simulated Exams and I took A LOT of practice quizzes and exams.
I downloaded the Rita M. book and read through it twice. It made more sense then the Velociteach materials.
A colleague recommended the PMP Master Prep dude who posts YouTube videos. I also watched some other videos if I was confused about a concept, process, etc.
I didn't even use the PMBOK Guide.
I also used the exam outline document/guide on the PMI website to show what they will test on in each process area. I went through that as I was studying materials and it clicked so much easier for me.
I can't stress enough how important it is to take practice tests, and the ones on the Simulator were VERY close to the real questions. I wish I had known that the first go around. Also, I didn't bother doing the formula dump before the exam started. I actually had memorized all the EVM and schedule formulas, and I barely needed them. I had maybe 2-3 of those types of questions.
By changing up my study method and materials, I studied about 3 more months to take the second exam. I passed with flying colors, getting Above Average on all process areas. I'm glad I passed too, I took the second one at the end of December, right before the materials and PMP exam was going to change.