Try this quick tip for keeping dark hair shiny. Chop some fresh rosemary leaves into a two cup heatproof measuring cup. Pour 1 cup of boiling water over and let steep for about 15 minutes. Strain out the leaves, a coffee filter in a small strainer works very well. Add a tablespoon of white vinegar and cool to room temperature. Wash your hair and condition as usual then use the rosemary infusion as a final rinse.
Rosemary brings out the highlights in dark hair and conditions the scalp to help prevent dandruff. If you're a blond you can use the same procedure with chamomile flowers. Calendula flowers will help bring out the auburn highlights in any hair color, especially those leaning toward an auburn hue. If you don't want to mess with straining the liquids ask your local Wholefoods market or herb shop if they carry heat sealable tea bags. You can purchase them online at Majestic Mountain Sage.