They recommend the following in order to give the person the best
chances of healing well:

• Call 911.
• Center yourself (e.g. take a deep breath, say a prayer, speak a mantra).
• Tell the person that the worst is over. Give him your name, and tell him
  you’re there to help. Ask his name and use it. Tell him the ambulance is
  on its way.
• Ask him, “Will you do as I say?”
• Be credible, confident, compassionate and concerned.
• Give him therapeutic suggestions. For example, “Because the ambulance
  is on its way, you can begin to take a nice, easy breath.” If there’s
  bleeding, tell him, “You’re bleeding just enough to cleanse the wound; you can send clotting factor to the area now.” If there are multiple injuries, or if you can’t tell where he might be hurt, “You can now allow all your body
  functions to start working toward repair and healing.”
• Remain calm and positive.

It’s equally important not to say anything negative to the person. Keep the focus of your words on positivity and healing. We all have a natural capacity to heal. Following this advice will help to trigger that capacity.