Most folks never do...but it is recommended as it will lengthen the life of the water heater.
Here is a step by step article on how to do it.
How to Flush a Water Heater: The Family Handyman
A few things to consider.....
1) on an electric water heater, you always want to turn off the breaker to the tank first, because if you accidentally allow the element(s) to not be immersed in water, if it is on it will burn out.
2) On many homes in The Villages, the plastic catch tank under the water heater sometimes is in the way of threading a hose on the drain sillcock. I wish the plumbers, when installing these water heaters would center the tank better so one could easily attach a hose to the drain...many times they do not.
Respectfully,
Frank