A leaking pipe can cause a lot of damage in a hurry. Basic household knowledge should include the simple task of shutting off the water, but do you know where your water main is? It is surprising how few people know what it is; let alone where to find it. The water main is usually located near the water heater or in a basement or your utility closet.
If you can’t find it call a plumber to come take a look. Once you have located it, you may need a wrench to turn it off. Keep it on a shelf or hook nearby so it is always at the ready. It also makes your friends think you know how to wield a tool.