I agree with Firekeeper: never let anyone else use your chrystals. If you use them on anyone, make sure you cleanse them well. Reiki, running water and burying them are all methods to use for cleansing.
A simple pattern using 4 chrystals: Place one above the head near the crown chakra. One by each hand. One between and just below the feet. Have someone activate the chrystals by striking gently the one above head, by left hand, the one between the feet and then the one at the right hand.
Always remove stones and chrystals after 10 minutes.
blackearth