Turn the electric off at the breaker. Check the wires going into the heater to make sure they are dead before beginning. Disconnect the wiring from the heater and mark them for installation later.
Shut the water supply valve to the heater. Open all hot water faucets in the house to allow air in the system and force all the water to drain from the tank.
Connect a garden hose to the drain valve on the tank. Take the other end of the hose and put it in a place that the hot water coming from it will not harm anything. Open the valve and allow the water to drain. It may take a little while to completely drain.
Remove the piping. If they are hard plumbed, they will have to be cut. If they are connected with unions, they will need to be unscrewed with a pipe wrench. If they are connected by hoses, they can just be unscrewed and taken off.
Remove the water heater to discard or use in another location.