A recent video from This Old House provides some helpful tips for dealing with common plumbing emergencies in the home. While most communities have qualified local 24 hour plumbers, it is helpful to control leaks and problems before the plumber can show up.
The discussion covered several common issues:
The leaking toilet. If a toilet is overflowing or leaking, the problem may be easy to solve using the provided shut-off.
The point is made that if the toilet is stopped, flushing will only make the problem of overflow worse.
Frozen or broken pipes. The most immediate way to deal with leaks from pipes is to find the master home shut-off valve. This will either be a handle to turn clockwise or a ball-type lever to stop the water flow. There are several modern compression connection devices that are often useful to stop the flow from broken pipes. Smart homeowners should keep a variety of these on hand for handling emergencies.
Water heaters. Either check the drain or the cold-water intake valves to stop leaks in the water heater until a plumber can get to the home. The point is made, however, to never shut off the temperature relief valve and drain.
These are useful hints to help the homeowner get control of a situation until a qualified local 24 hour plumber can arrive to provide a permanent solution.