The answer to this question depends so much on the circumstances. What do you have with you? Where are you? What kind of knowledge do you have? What can you tell by looking at the person? All of these variables affect what I would do.
The first thing I would do is consider whether this might be a completely benign situation. What if the person is simply lying on the floor asleep? I would not be surprised to walk into my living room, for example, and see someone asleep on the floor. So my first thought would be to try to determine whether the person could just be asleep.
Let’s assume that I think that the person is not asleep. Now, the answer depends on other variables. What if I work in the medical profession? If I were a doctor, I would then examine the person to see if I could determine what might be wrong with them. What if I have a cell phone with me like almost everyone does these days? If I have a phone, I will call 911 and tell the dispatcher what is happening. That person will likely tell me what I should do until help arrives. If I don’t have a cell phone and there is no other phone in the house, then the most logical thing (if I am in a town) is to go to a neighbor and ask them to call 911 for me.
These are some of the things I would be likely to do. However, a person’s exact actions would depend very much on any number of variables that are not provided to us in this question.
look to see if the person is hurt/breathing.... if not do CPR if you know how, grab a phone and call 111. if the person if hurt take your shirt of and wrap around wound or get them in a comfortable position.
First I would check if the person is breathing or maybe asleep. I would do that by lightly shaking the person calling their name. If I get no response I would perform CPR and/or call 911.
First, check and see if the person is breathing. If they are, and are not asleep, check to see if they are wearing a medical ID bracelet or necklace. If they are breathing, do CPR, and call 911 immediately. If you do not know how to do CPR, you still need to call 911 as soon as you can. If it is the worst-case scenario, and you do not have a phone on you, run as fast as you can to an adult or another peer.
I would immediately assume that it's Shia LaBeouf and run for my life.