The first hard freeze usually shows up before most people are ready for it. The good news: the jobs that prevent most cold-weather plumbing trouble are simple, cheap, and can be done in an afternoon. Here's the short list.
1. Unhook the garden hoses
A hose left on an outside faucet keeps water trapped in the faucet. When that water freezes, it can crack the faucet or the pipe behind it, inside the wall where you won't see it until it thaws and leaks. Frost-free faucets need the hose off, too, or they can't drain. Disconnect every hose, drain it, and store it.
2. Shut off and drain outside faucets
Many homes have a small indoor shutoff valve for each outside faucet, often in the basement, crawlspace, or a utility room. If yours does, close that valve, then open the outside faucet so the line can drain, and leave it open for the winter. Not sure what you have? A foam faucet cover is an inexpensive extra layer of protection, but it isn't a substitute for draining the line.
3. Find your main water shutoff and make sure it turns
If a pipe does burst, the main shutoff is what stops the damage. Find it now, clear a path to it, and show everyone in the house. A round wheel handle usually turns clockwise to close. A lever handle is a quarter turn; when the lever sits across the pipe, it's closed. If the valve is stuck or leaks when you turn it, don't force it. Have a plumber look at it. More on this in Know where your main water shutoff is.
4. Insulate pipes in cold spaces
Pipes in crawlspaces, unheated garages, attics, and along outside walls are the ones that freeze first. Foam pipe sleeves from the hardware store slip right on; tape the seams and cover elbows as well as you can. Seal gaps where cold air blows directly on pipes, and keep the garage door closed on cold days if water lines run through the garage. If you're thinking about heat cable, follow the maker's instructions exactly or have a pro install it.
5. Plan your cold-night routine
On the coldest nights, a few habits make a big difference. The American Red Cross recommends opening kitchen and bathroom cabinet doors so warmer air reaches the pipes, letting cold water drip from a faucet served by exposed pipes, and keeping the thermostat at the same setting day and night. If you'll be away, leave the heat on, set no lower than 55°F.
6. Know what to do if a pipe freezes anyway
If you turn on a faucet and only a trickle comes out, suspect a frozen pipe. Leave the faucet open and warm the pipe gently: a hair dryer, an electric heating pad, or a space heater kept well away from anything that can burn. Never use a torch or any open flame. If you can't find the frozen spot, can't reach it, or it won't thaw, call a licensed plumber.
If a pipe bursts, shut off the main water first, then call for help. If water is near outlets, cords, or your electrical panel, stay out of it and call a pro.
Keep it on paper
Checklists beat memory, especially when it's cold and you're in a hurry. The Winterizing Checklist walks through all of this room by room, and the Frozen Pipe Sheet is a one-page "what to do first" for the fridge.
From the shop
General homeowner info, not a substitute for a licensed plumber. Gas, electrical, and anything beyond basic work are jobs for a licensed pro.