Only let someone who knows what they are doing launch the rockets.
Always launch rockets at least 7km away from an airport so that you don't interfere with the landing or taking-off of planes.
Always launch in a wide open field with lots of room so that your rockets won't land in traffic or in trees or on houses.
Always stand at least 20 feet away from the launch pad so you have time to react if something goes wrong at the pad.
Always keep your eye on the rocket.
Never put anything other than recovery wadding in the rocket.