What has your instructor said?
Short answer - Anything that could be used to check that you are safe and competent to operate that aircraft as it's Commander.
Aircraft Technical - Limitations, Check A, CoG/ Mass and Balance. Aircraft systems, Emergencies.
Airmanship - Met, Nav, Aviation services - METAR,TAF, Notams, ATIS - if they're relevant. Basic air law. Procedures at your home airfield.
It's potentially an endless list. That said try not to worry about it too much. There shouldn't be trick questions - just those that will assure the examiner you are a safe and sensible pair of hands.
The standard rule of thumb is " Would I trust this person to fly a member of my family"
Good luck and enjoy.
