The reason why there is a high failure rate is because people don't adequately prepare for it. Its not difficult, but you have to put in the time and study the large amount of information covered.
Get the Securities Training Corp study guide and order the practice exams (disk or online, NOT paper). Read the breakout of what percentage of questions comes from each section - its accurate. Read the entire manual once through, then take the practice exams (you will be borderline passing to failing). Re-read the manual, but this time hi-lite what keeps showing up in the exams. Then re-read your hi-lited material. You must be thorough in munis, options, and secs laws.
After your second read, retake all of the practice exams. You should be passing to slightly higher. Finally, read your hi-lited material one last go through, then take the practice exams as many times as you can. You should be scoring 80's as a minimum. I recommend taking the exams 3 times. The disk/online exams give explanations as you go, very helpful.
Money-back guaratee you will pass if you follow this study program. Its overkill, but it ensures you will pass.