The secret in activation and comprehension lies in asking good questions and looking for their answers. If you want to ask good questions you need to have a purpose. Know where you are starting from and know where you want to finish.
The funny thing about the PhotoReading system is that the PhotoReading step itself is the easiest to grasp. There's nothing to it and chances of doing it wrong are slim. The important part of the course people seem to skip the most.
The important part is to look at the book in your and and ask yourself What is in this book for me? What's my purpose? What do I hope to gain.
Check the bullet points on page 24 of the PhotoReading book (4th edition PG 25 3rd edition).
AlexK