How do you replace a hot water heater?

A general map to replacing a hot water heater begins with shutting off the gas or electricity and letting it cool. Then shut off the water supply to the unit. Open a hot water tap high in the supplied (yes, supplied) line so air can get in and reduce water leakage. Then drain the unit. Then uncouple the inlet and outlet water lines. Have used soaker-upper towels handy. Your failure to properly drain the unit will appear in a nasty way if you don't think through the part about draining the unit. Then disconnect the power from the unit after insuring that it is, in fact, de-energized. Or double check that the gas is shut off and remove the gas line from the unit. If there is a stabilizer strap about the unit, remove that. (If there wasn't a strap, you're gonna put one in when you install the new unit, right? Yes, you are.) Pull the unit. Replacing the unit is a reverse or this process. Double check electrical connections to be sure they are snug without over-torquing the fasteners. Or be sure to check for gas leaks with a spray bottle containing soapy water. This is critical. You blow this, you may end up dead. Or your family. Be patient and work cleanly. Don't hesitate to call a handyman if any of this sounds like a foreign language. Ask questions at a place that supplies hot water heaters, like the so called "big box" stores or a good hardware store. Consider going to a local bookstore (new or, if possible, used) and peruse a book on home repairs and upgrades. Do yourself and the bookseller a favor and actually buy the book if you find one with the information you need. Be smart about this. Shortcuts and errors can cause failures that can kill you and/or family members or damage property in a big (expensive) way. You have been cautioned, and because you are smart, a Word to the wise is sufficient.