I really like Aveda's Detoxifier shampoo, but mostly for the intense herbal scent. The best way I clarify my hair is to saturate my hair with a mix of:
12oz beer (cheap is good)
12oz warm water
4oz apple cider vinegar
I run this through my hair repeatedly for 1-2 minutes and massage my scalp. Then I lather in my clarifying shampoo, wait about 30 seconds, then rinse thoroughly. I deep condition afterwards for at least 20 minutes. This combo pulls every bit of buildup and styling **** out without drying my hair.
I do the beer mixture + clarifying shampoo about 1x per month, and do 1x weekly just the clarifying shampoo.