I have been making my own shampoo for nearly 10 years now.  I also make it for friends and family.  Here it is:

1. 1 cup of fresh rosemary (not dried)
2. 2 cups of distilled water (not tap) the water has to be pure water with no chlorine added.  Chemicals will distroy the benefical properties of the rosemary.
3. 1 12 oz or larger of unscented castile soap (if you are unable to find castile soap, baby shampoo is the closest thing to the castile soap).
4. Add the rosemary to the water in a saucepan or you can put in the microwave.  If you use the microwave, put the rosemary and water in micro-safe bowl and nuke for 5 min.
5. After the water and rosemary has come to a boil, remove pan and cover allowing it to steep for 10 min.
6. Strain rosemary tea and remove the rosemary stems.  Add the castile soap or the baby shampoo, which ever one you used. 
7. Put into bottles (you can use the bottle the shampoo came in or find some glass bottles and use them.
8. Let them sit over night before you use them, you can add essential oil to them if you like.

You will get two bottles of shampoo.  The first time you use this shampoo you will not get any suds (which is a chemical that is added to comercial shampoo products), rinse and shampoo a second time. 

Also, the shampoo will be very thin so you will have to pour it directly onto you hair instead of into you hand.  After you shampoo you will notice that your hair is real shiney and more managable. 

You will also notice after several time of use that your hair is darker and thicker and maybe even longer.  If you have gray hair, you will no longer have gray hair.  This is an added benefit of this shampoo.