I guess you could say I've had a relationship going on for the last few months with PMI's Agile Certified Practitioner test. I was among the set of people who took this test in its beta last year and (finally!) heard in January that I was among the first to achieve this certification. At the same time, I was teaching the 3 day prep class for the PMI-ACP. So here's what I would say about my experiences on both sides of the test and the training.
First, I would suggest that taking the 3 day prep class is really helpful for passing the test. This certainly worked for me though I was teaching the session (which is a great way to learn). I went and took the certification test very shortly after my first prep class session. After all, it seems like you should have a certification if you're going to teach it!
Anyway... the class was really a big help and a solid learning experience. Since the so-called AgileBOK (book of knowledge) is not yet out, you have a few choices on how to study up for the PMI-ACP:
1) Read a lot of books. A LOT. PMI recommends 11 books for test prep. Among these is the The Software Project Manager's Bridge to Agility by our very own Stacia (Broderick) Viscardi! The books that are listed are all very good and are highly recommended reading. But reading them all will take a while and maybe you'd rather approach them at your own pace instead of as part of a push toward achieving certification. Note: There is also at least one PMI-ACP specfic study guide available now with fairly good reviews.
2) Look at study tips out on the web and take practice exams that are also available (for a charge). These test reports and tips are easy to find - just search for something like "PMI-ACP study tips" and you'll come up with quite a few. A number of people have reported that the practice exams at www.AgileExams.com were also very helpful though I did not use them myself.
3) Take the prep class. OK, this is a significant commitment of time (3 days) and money, but it really is an excellent way to prepare. There are some very specific pointers that will help you with questions that show up on the test. And it's more than just a test prep - the class is a great overview of current Agile and Lean practices and thinking. And some places (like AgileEvolution) are even combining this with existing Scrum training so that you can achieve CSM certification and PMI-ACP prep in a single session.
So what should you do? I may be slightly biased, but my recommendation is a combination of all of the above. You should read at least some of those recommended books. Focus on areas where you might be less experienced. In my case, I found that I had the most trouble with some specific XP questions that were on the test. Happily, it wasn't enough trouble to keep me from being "proficient" in all the areas, but it's an area that I would focus on more if I was doing it again. By all means, read the study tips you can find on the web - there are some very good pointers there. And if at all possible, take the prep class. I think you'll find it both interesting and a good use of your time.
What we see as trainers of the PMI-ACP prep class is similar to what we see in many other certification-focused classes: a real mix of experience and expectations from the students. There are students who are very experienced and coming in focused on passing the new test. Others who have little Agile exposure are just using this class as a way to learn. The good thing is that the class works for both: it's broad in coverage but specific in many key practices. And there's a lot of exercises to really help you learn and to make it all more fun.
While there are an increasing number of certifications in the Agile world, PMI always brings significant rigor and credibility when it introduces something like the PMI-ACP. The PMI may have been late to the party, but they've introduced a certification that will likely become very popular and may be key for some folk's career advancement going forward. I hope you'll seriously consider the PMI-ACP and its prep class - maybe we'll see you there!