Real emergencies happen outside of the hospital. In addition to calling for help (either phone 911 or ask someone else nearby to phone 911), here are some simple skills you can learn that can help save a life.
If someone is unconscious and they did NOT just have any kind of trauma, you must find out if they are breathing and if their heart is beating.
To find out if the person is breathing, lie the person down flat on their back and listen through their mouth/nose to hear if they are breathing or look at their chest to see if it is rising. Here are some reasons why they may not be breathing and what you can do about it:
2) their brain stopped telling them to take breaths - if you can, push air in side their lungs for them, use a barrier device when possible (e.g. pocket mask)
3) their lungs are filled with something else - tilt the person on their side to "pour" some of the fluid out for a few seconds
You should always assume the person does not have a pulse unless you can prove otherwise. Therefore, if you don't know how to check for pulses or if the person does not have a pulse, immediately start pumping their heart for them. Here is a video on how to do that while also breathing for the person until professional help arrives:
http://www.youtube.com/watch?v=IUB0Ep4DuBI
Stay tuned on what you can do if someone is unconscious after an accident or trauma!