1. Check if the victim is alert by shaking or tapping the person gently on the shoulder, if the victim makes some movement or noise shout 'are you OK? '
2. If there is no response shout for help and send someone to call emergency services. If you are alone, call emergency response and retrieve an AED (if available), even if you have to leave the person.
3. Carefully place the person on their back. If there is a chance the person has a spinal injury, two people should move the person to prevent the head and neck from twisting.
4. Open the airway. Lift up the chin with two fingers. At the same time, tilt the head by pushing down on the forehead with the other hand.
5. Look, listen, and feel for breathing. Place your ear close to the person's mouth and nose. Watch for chest movement. Feel for breath on your cheek.
6. If the person is not breathing or has trouble breathing: Cover their mouth tightly with your mouth. Pinch the nose closed. Keep the chin lifted and head tilted. Give two rescue breaths. Each breath should take about a second and make the chest rise. Perform chest compressions: Place the heel of one hand on the breastbone -- right between the nipples. Place the heel of your other hand on top of the first hand. Position your body directly over your hands. Give 30 chest compressions. These compressions should be FAST and hard. Press down about 2 inches into the chest. Each time, let the chest rise completely. Count the 30 compressions quickly:
7. Give the person 2 more breaths. The chest should rise.
8. Continue CPR (30 chest compressions followed by 2 breaths, then repeat) until the person recovers or help arrives.
9. If an AED for adults is available, use it as soon as possible.
10. If the person starts breathing again, place them in the recovery position. Periodically recheck for breathing until help arrives.

Source http://www. nlm. nih. gov/medlineplus/ency/article/000013.htm.

Attribution: Avallain