These are rules set by your state, not by BeaterBoss, so they differ from place to place. Your state’s page lists what a seller there has to do: find your state.
Your plates
In most of the states we have checked, the plates stay with you, not the car, so you take them off before the tow truck leaves. Ohio law, for example, says to take them off as soon as the car is sold. Many states then let you move them to another car you own, keep them or turn them in.
In a few states the plates usually stay with the car. California, Delaware and Minnesota are among them.
Your registration and insurance
In some states you turn in the plates or cancel the registration first, and only then cancel your insurance. Doing it the other way round can cost you. New York, for example, can suspend your registration and your license if you cancel the insurance before you turn in the plates, and Nevada can send a fine for a plate that is still active with no insurance. Delaware, Georgia, Maryland, North Carolina and Washington, D.C. also put the plates or registration first.
On pickup day
Take out your things, and take off your plates if your state has you keep them. Pickup day and getting paid has the rest of what to have ready.