Ask the stone's permission for the healing, as well as the permission of the person's spirit that you are working with. Then, open your heart chakra and focus on the healee. As you lay the stones on the corresponding areas of the body that need healing, listen to your intuition. If your instinct tells you to place a green stone over the heart chakra, do. If you are reading the person's aura and see that their aura is a nice green color, but there is a yellow spot that looks imbalanced, you might want to place a blue stone there until there is a balanced green throughout the auric field.
Visualization is an excellent companion to crystal healing.
Visualize the aura smoothing out and vibrating with a healthy glow. Along with visualization, there is sound. Sound creates color. You will notice in the list above that there is a note beside each of the areas on the list. These two things, visualization and musical notes, increase the vibration of the color and strengthen the healing properties.