Shampooing: The idea of cleansing is to remove sebum (oil) and products from the scalp and hair. Starting with a quarter-sized (or dime-sized for short hair) amount of shampoo and slowly massage the product into your scalp and hair. Massage in for 30 seconds or longer. A second shampoo is not always required, it all depends on the condition of your hair, an of course your own preference. Oily hair may require a second cleansing. Some people prefer to shampoo everyday. For others that may be to damaging.
Water alone can cause damage to hair and can also cause color treated hair to fade. Oily hair needs to be cleaned more frequently, but people with dry and damaged (Color or Premed) hair should extend the time between shampooing. Shampooing washes out the natural oils that protect hair. Conditioners can replace some of that moisture lost.
Rinse: Rinsing your hair may seems simple, but the fact is the majority of people do not rinse thoroughly, leaving hair with residue of their shampoo and conditioner that can cause and oily build-up on their hair. Rinse while working your fingertips through your hair for about 30 seconds should do the job.
These steps are just a guideline, you should be able to determine what is best for your own hair by the results you achieve.