Don't forget to shut off the power and the water before you drain too! Also, once you shut off the water and the power, if the valve won't open you can bleed the pressure out of the tank by opening the relief valve on top and drain the tank by removing the lower element.
Often times the valve will be plugged up. Unhook the hoses and use a coat hanger to unplug it.
I'd never suggest draining it by removing the element unless you use a hand cart to get it outside first or your going to have all that water coming out at once with no way to stop it.