My teacher Inamoto Sensei says, "Place your hands, surrender, smile." That is his instruction for sharing Reiki with another person.
What this means to me:
"Place your hands;" well, that's simple. Reiki is simple.
"Surrender:" release any attachment to the outcome. Surrender your ego.
"Smile," because now you're in the flow of universal life force energy. Reiki is bliss.