To form questions.
Step 1 prepare... this is important you need to have a purpose without a purpose you don't have a foundation for asking questions.
Step 2 preview. Keep it short. 60 seconds max.
Step 3 PhotoRead.
Step 4 POSTVIEW (the 4th edition of the book has this emphasised as an extra step. The 3rd edition has it as part of the PhotoReading step. It has been separated to clarify it's importance.
Okay so why is postviewing important? This is where you check your purpose. build your curiosity and start by finding two or three questions you might like answered.
Postview is like preview. You open the book every 20th page or so, Pull about 18 to 25 trigger words and write down a couple of questions. Then you leave the book to incubate.
You don't have all the questions you will ultimately seek answers to. Haven't you noticed that in learning one question answered leads to another question asked?
Postview no more than 15 minutes. My classes are limited to 10 and they always find the starting questions.
AlexK