Today was my day to clean the water heater. I recommend to do this once or twice a year. I try to do it in the spring and in the fall.
Turn off the power.
Hookup a garden hose to the hose bib at the bottom of the water heater and run outside, to a drain, or into a bucket, anyplace that is lower than the water heater.
Close the cold water inlet.
Open the hose bib at the bottom of the tank.
Open the temperature and pressure relief valve at the top of the tank. This relieves any vacuum and allows the tank to drain.
Drain the tank till the water runs clear. You should see some orange, rusty water. There won't be much if you do this regularly.
Reverse the steps to put the tank back in service.
If you do this regularly your tank will last longer and if you need to salvage the water from the tank for drinking you will have more potable water and less orange sludge.