Want To Have Clean Hair:

 It's perfectly natural to want to have clean hair, but as a rule of thumb, most dying products call for you NOT to shampoo for a period of time before you dye. 

This allows the color to better adhere to the built up oils in your hair. One thing you can do a few days before you dye is submit your hair to a deep conditioning, as this will add a ton of moisture that the dye loves.