Wash your hair with some shampoo. You want to work with clean hair free of oils and hair products. Brew about 2 cups (470 ml) of strong, organic coffee. It may help to brew 2 cups (470 ml) of coffee, since you will be pouring the coffee over your head as a rinse. The more coffee, the easier it will be to pour on your hair. Allow your coffee to cool down to room temperature, or even cooler. Once your coffee is brewed, pour the coffee into a large bowl or pot. Essentially, you need a large enough container to hold the coffee so you can scoop it up to pour on your hair, and also to collect the falling coffee as you hold your head over the container and pour the coffee on your hair. Place the large bowl or pot into the shower and hold your head over the bowl. You can dunk your hair into the bowl, and use a small cup to scoop up coffee and pour it over the rest of your hair. This will be especially helpful to reach the back of your head, which will be unable to be dipped all the way into the coffee. Pour coffee over your hair approximately 15 times. This will make sure your hair gets completely saturated with the coffee. Wring out your hair, and allow the coffee to sit on your hair for about at least 20 minutes to a few hours. It may help to pin your hair up in a bun to prevent the coffee from dripping. Alternatively, you can pour the brewed coffee into a spray bottle and spray your hair. Either way, be sure to cover as much of your hair as possible with the coffee. After you have let the coffee sit on your hair, rinse out the coffee with water in the shower.  You may need to soak you hair with coffee a few more times in order to achieve your desired hair color. Rinsing your hair with apple cider vinegar may help the coffee color last longer.

Summary:
Shampoo your hair. Brew coffee. Transfer the coffee to a large container. Rinse your hair with the coffee. Rinse your hair clean.