Keep them against the wall with screws or brackets near the top of the unit. Don't put flammable materials anywhere but on the bottom shelf. Learn how to shut off your own gas, water and electricity. If any connections break inside the house, or even where they enter the house, you have a problem. Your local utilities office will help you find the valves for gas and water, and they'll also warn you not to try to turn them off unless you're certain that a break has occured.
Circuit breakers are generally in the basement, or under the stairs.
Find yours before an emergency arises.