I will give you some tips and hints to help you complete you PMI ACP i.e. Agile Certified Practitioner exam in the first go.
Step 1) Real life experience:
I agree with PMI's criteria that we need to have 1500 agile project experience. It gives you good knowledge about how things can go right or wrong practically. So if you do not have that real life experience, then please get it. It really helps you to solve atleast 20% of the PMI ACP exam questions.
Step 2) Classroom training:
This 3 day training was also important to know some unknown things in agile, lean and kanban.
Step 3) Books:
My main study guide was the book from Mike Griffiths: PMI-ACP Exam Prep. I read it three times.
First I read the book in fast pace. I focused on headings and diagrams. After reading each chapter, I also solved the exercise at the end of the chapter. For the first time I got only 50% answers correct.
Second time I read the book in full details. I also carefully read those sections, for which I got wrong answers in the first time exercise. Then I solved the exercise and this time I got 70% correct.
Third time I read the book with 100% attention to each and every word. (remember to read each and every word) Now, this time I got 100% correct answers when I solved the exercise (may be because I would remember the answers by then).
Step 4) Solving the online exams:
Each time I completely read the book, I also solved questions from below links. Some of those are free and some of those are paid. I recommend to solve free ones first :) Paid ones are also equally worth. Paid ones cost you from $3 to $10, which is worth than not doing it & putting $495 at stake. From free ones, I got approximately 20% similar questions in my exam. From paid ones like examprofessor, I got approximately 30% similar questions in my exam. edward-designer link is like a composite of all the online guidance. Remember the questions are not exactly same. Those are similar and you will get fair idea of the difficulty level and also you will get to know your gaps.
First read the question carefully and understand grammar of it. If it is easy, solve it. If you are in doubt, mark it and go to the next question. After you solve all easy ones, solve the marked ones. This should leave you with 30 minutes. Now in those 30 minutes, review carefully each answer of all those 120 questions. I am sure you will change answers of at least 5 questions (because your brain keeps on thinking).
Out of 120 questions, I was able to solve 80 questions with ease. Those werevery straight forward (based on my knowledge and experience). 20 questions were little tricky, but if you think twice, then they were reasonable. Rest 20 were very difficult and I had to spend 1 hour to solve those.... and I am sure I might have scored 0 in those 20.
Suggestion: Apart from the suggested book above, also read other books on lean, kanban and XP. Also browse one website related to these topics daily. This will help you to solve those 20 tricky questions.