There are toilet ways to combat this water damage disaster. Let's talk about the four steps you can take, to prevent this from happening to you and your family.
When you get to the house stand if front of the toilet and locate the water shut off valve. Should be down below the toilet on the wall. Just turn it off (righty-tighty) completely and flush the toilet. All the water should have left the tank, well at least most of it. If there is remaining water line repair get it out with paper towels or a rag. The important thing is that no more water came in. If it did then your valve is not shut all the way or not working and you need additional help.
One other common design that is considered "washerless" was made famous by Delta and copied by several other makers. It uses little "cup" seals that fit over springs recessed in the back of the valve body. The springs press these "seals" against the cartridge and regulate the flow through little tapered openings in the cartridge. If you have one of these and it's dripping, changing these springs and seals will usually correct it. Here's a tip. Once you have the cartridge out of the way, insert a phillips screwdriver into the seal and pop both the seal and spring out. Stick the new ones on the end of the screwdriver to help guide them into place. This is especially helpful if you don't have long slender fingers.
Working on the gas lines is also a complex job that only a licensed plumber can handle because it is very dangerous. Small leaks can't always be detected by odor alone, but a licensed professional has the proper equipment that's needed to ensure that you don't have any leaks in the line.
Here are some general cautions. Do not begin jobs on holidays, weekends, or at times when plumbers raise their rates or are difficult to reach. Do start early leaving plenty of daylight to call a plumber if something goes wrong. Study the situation carefully. Think about what might happen if something suddenly broke and what the effects would be. Old corroded copper tubing might break in the wall when you are wrenching an angle stop that supplies the water line repair to your toilet. A flood in the wall could be costly. If the angle stop, on the other hand, is new and shuts off easily and you have another toilet in the house then it might make sense to repair the toilet yourself. Be honest, too. Are you handy with tools? Did you do well in shop classes in school?
The work area should always be clean and free of trash and clutter. The cleaner and less clutter there is in a Plumbers' work area, the better able a plumber will be to make sure that his job goes as smoothly as possible.
Water leak detectors can keep your home safe. They can give you the peace of mind knowing that you won't come home to a house full of water. It is a lot less expensive to buy a water detector than it is to pay thousands of dollars in home repair costs.