Flushing, or draining your hot water tank, is a maintenance task most home owner can perform themselves. It's a good idea to flush your hot water tank at least once a year. This can help extend the lifespan of the unit and help maintain maximum energy-efficiency.
Refer to your hot water tank's owner's manual for instructions on how to flush your hot water tank. If you are unsure how to do it, contact a local licensed plumber.