Buy a litre of Castile soap. Most health food stores carry this.
Boil 2 cups of water with 1 tbsp rosemary, 1 tbsp sage, 1 tbsp thyme. Once boiling temperature is reached, remove from stove and add 1000 mg of MSM (a supplement available at most pharmacies - MSM is sulfur which aids absorption of the herbs in the shampoo into the scalp). Let herbal tea and MSM steep for 20 minutes and mix with a 1 part herb tea/MSM mixture to 2 parts castile soap. Add chamomile or other herbs as required. Store in fridge and use within 1 week. I use air tight portable containers to store mine in 3-4 use portions. These can be frozen as well.
This shampoo is lovely on your hair and the cost for such a pure shampoo is worth it (and it costs less than most 'organic' and 'natural' shampoos on the market).