For one thing, you have an excellent study guide and outline. That is the Private PTS. Start there. Make sure that you know each item in each Area of Operation cold. The FAA books and other references for each item are listed. Despite rumors and opinions to the contrary, the examiner will expect you to answer every question by reference to these materials. These materials, such as the Flight Training Handbook and Pilot's Handbook of Aeronautical Knowledge, are the FAA's final word on what it expects you to know. Plenty of folks who've come before you haven't believed that, and have busted their orals because of it.
Know the POH for your airplane forwards and backwards. Know all the systems and limitations of the airplane. All that information is in that section of the POH. Know the numbers of your aircraft. You should have known them even before you started flying. Chances are, your instructor gave you a little written exam or had you fill out a questionnaire about your airplane.
Know Parts 61 and 91 of the FARs. Know currency. Know medical certificates. Know all the pubs, especially the A/FD.
All these are examples. Others will have more suggestions.
Your instructor should be giving you a practice oral before he/she signs you off for the practical. If your instructor is on the ball, the oral he/she gives you should be far tougher than the oral you get from the examiner.
Hope all of this helps. Good luck with the flight test.