The two most common ways are the use of a water restrictor in the shower head, most of the heads in the U.S.A are equipped with a water restrictor. Secondly, the commode water tanks have been made smaller using less water per flush. Some conservation of water may be gained by using "instant" water heaters in the shower/bath and basin rather than a hot water tank type heater. Locating an instant water heater near the output of the water reduces the need to let the water run until it becomes hot at the output. I hope that this is the answer that you were looking for and it has helped you.
