The importance of checking the brakes before and after engine start is critical. If a break pedal can easily be pushed or falls past the extension of your ankles. Don’t start that airplane! Instead have it checked out by an authorized A&P (Airframe and Powerplant) or IA (Inspection Authorization) mechanic.
Positive exchange of flight controls is a “Special Emphasis Area” that the FAA has deemed critical to flight safety. When exchanging flight controls the student or instructor (person gaining control) will say “I have the flight controls” the relinquishing person of control will say “you have the flight controls” then the person gaining control will repeat “I have the flight controls”. This method allows the flight crew to truly know who is flying the airplane.