A push mower is small but it holds gas and oil that will leak if you tip it wrong, and the fuel is a fire hazard. Drain or empty the fuel, disconnect the spark plug, and keep the mower upright with the correct side down to avoid oil in the air filter.
Pro tip: Running the tank dry is the simplest way to eliminate fuel leaks and fire risk for the move.
Watch out: Gasoline is flammable and the fumes are hazardous, so empty the tank and disconnect the spark plug before transport.