DEs job is to ask you things you should know and that material is outlined in the "PTS" Practical Test Standards. Guides like ASA Private Pilot Oral Prep Guide help prepare for the exam.

I have not encountered an examiner who required exhaustive memorization. I hear the inital CFI checkride is an exception to this, but in 4 checkrides none disallowed an occasional referencing of books during the exam. In any case a DE knows you can look something up, so the only question is do you know where to look. As soon as you tell them where the info is found, assuming it is of the order of minutia and not basic material, they do not count it against you.

On the other hand for your basic material which there is quite a bit of, such as day vfr equipment, night vfr equipment, airworthiness requirements etc., you may want to make some acronyms to help retain those lists and be pretty good at remembering what's on them.

If you are going for your private pilot exam and do not know the requirements, definitely study it some more. That is mostly found in the PTS.