If you are experiencing loss of water throughout your home the first thing you should check is the main water shut off valve and make sure it is fully in the on position, the shut off is typically located in your garage, but can be different depending on where you live. If the main shut off valve is completely turn on but you still don't have water then check to make sure there are no breaks in your main water line, if there is please call your plumber for further assistance. If you are experiencing no water flow at only one faucet then first check to make sure the supply line is turned on, more than likely you have one of 2 types of shut off valves: a twist turn to open and close the valve or a push-pull. If your supply lines are in the on position and you still don't have any water flow then check to make sure there is no sediment build up in the aerator, if there is then removing the sediment should restore water flow. If you still do not have water flow then you should call your plumber for further advise.