If you see (or hear) evidence of a water leak the first thing you should do is find the main water shut off valve to your house and turn it off. Sometimes this is found near the street where your water meter is or often times there is a shut off valve near an outdoor spigot. If it is a toilet or kitchen sink that is leaking just turn off the valve that is feeding it.
In Florida we normally see an average life expectancy of 10-12 years due to the aggressiveness of the mineral content in our water. If your water heater is leaking be sure to turn the valve off to the water heater and shut your circuit breaker or gas valve off.
The parts within the toilet tank (flapper, fill valve) often wear out within a year or two and simply need to be replaced. All of the working parts can be replaced without having to replace your toilet.