I hope this post helps those on the journey to Practitioner. There is a  lack of resources on this test. It is also difficult. Do not  underestimate it.
The book is packed full of wisdom. It has  become one of my favorites. Not because it's a good prep book... but  because it's a fantastic resource.
Unfortunately, you are not  tested on wisdom. You are tested on how specific statements in the book  match a given scenario. You must read a given sentence and recall (for  example) that "communication is two way" or that we must "design for  experience" ... and so on. What makes this challenging are the vague and  often invisible assumptions. I hate to say this, but I will say it  anyway. You must study hard, because the Practitioner exam is so poorly  written.
Here are my tips:
For CSI, memorize the specific  outputs of each step. Also know the tools in each step. The book is NOT  explicit here. Know that some questions will work backward from the  tool. For example, you might have to infer that 1) the 
business case is used to obtain agreement; 2) stakeholder agreement is cemented in 
"where do we want to be?"; 3) ...and so on. You must map out CSI in your head. Here is my outline: 
https://imgur.com/91nUOze
For  OCM, be aware of the order within the Stakeholder Management (Identify;  Prioritize; Understand; Plan) and Empowerment (Identify (TNA); Plan  (Plan); Do (Train); Measure). Again, the book is not explicit here. Here  is my outline: 
https://imgur.com/91nUOze
Know your metrics well. The book could have been more visual with these. Here is my outline: 
https://imgur.com/7KLngpZ
Know  the meaning of "adopt and adapt". Know the difference between outputs  and outcomes. Know how it ties in with VOCR. Be able to identify the  specific V, O, C and R given a sentence containing these elements. You  will be tested on detail.
Know the tools in Chapter 7. I  recommend filling out EVERY template, using your current work situation  as a basis. Then do it AGAIN, using Axelos' case study as a basis. Use  your imagination to fill an blanks. By the way. The case study in the  sample paper is the same as on the test, so memorize it!
What do  you NOT need to know? Items that won't appear include the Stages of  Grief, Gartner Hype Cycle, COBIT, etc. They are inside the book but  outside the syllabus.
For prep material, you need the official  book and free sample papers. That's it. I do not recommend  instructor-led training. The book is clear and concise enough that none  is needed. In fact, I couldn't find a course that truly complemented the  book. It only wasted time and muddied the waters. Of the courses I  surveyed for my company (both online and offline), all were dismal.
In  short... Practitioner is a good product. The book in particular is  fantastic. The test is tough, but for the wrong reasons. Read the book  carefully. Read it at least twice and do the practice exams. If you're  doing this with a group, scheduling a few chapters per week and using  each tool (as they come up) on a real problem works wonderfully. My  group read "Phoenix Project" in parallel which made the experience more  enriching.
Good luck future Practitioners,