Always shampoo the hair and scalp twice. A euro sized amount of shampoo is more than enough. Create a lather in the hands and pop it into the scalp. Spend 30 seconds massaging the scalp, ignoring the hair. After the 30 seconds rinse well. 

Your second shampoo should be half the amount of product. Again, lathering into the hands and straight onto the scalp, this time you should get a much greater lather even when using half the amount of product. This time involve the ends of your hair very gently and leave for two minutes, bringing under the hairline. Rinse well.