How to choose a shampoo?

If you struggle at the time of buying a shampoo, or you wonder how often you need to wash your hair, or the correct technique... you are not the only one!
At the end of this post we hope you know:
What type of scalp you have, and why it is important
What type of product you need to clean it, and how to use it
What ingredients you can aim to find
First of all: it should be the scalp the one which dictates which product we are going to use to wash the hair. We use shampoo to clean the root area, we do not put shampoo in the middle and ends of the hair (normally). Learn a good washing technique here.
Ask yourself:
1. How is your scalp?
Normally, if you feel you need to wash your hair every 1-3 days, we tend to consider it oily.
If it is dry, it would look flaky, dull, even have small cracks. Sometimes it may feel itchy, or you can have small loose pieces of dry skin (do not confuse them with dandruff!).
If it is in the middle of both, we would consider it medium or average. You may wash it 1-2 per week, maybe when it gets dirty it may be a bit itchy and get oily.
2. How often are you going to wash it?
This question is related with your life style. If you do sports, or you spend a lot of time in the kitchen, for instance, you are going to tend to wash your hair more often. Therefore, regardless of your type of scalp, you would need to wash it more gently.