What Procedure Should I Follow To Replace The T&p Relief Valve On My Hot Water Heater?

Put the gas valve in the pilot position so it doesn't call while you're working on it. Shut the cold and hot shut offs ( if none,then shut the main to the house to stop the flow of water to the water heatr. If only a cold shut off then close it). Get a hose or bucket and drain the water from the drain on the bottom ( usually made of plastic or brass). Drain it until you can open the releif by lifting on the lever attatched to it and water doesn't come out. Unscrew the old releif, tape and dope the new releif. Screw it back in and reconnect the blow down tube. Open your water valves, put the gas valve in the on position( the main burner will come on because of the cold water you are putting into the water heater. Open the faucets to purge them of air.