What are the three steps for proventing shock and for giving first aid for shock are?

It depends how many injuries the person has in the accident. DO NOT MOVE THE VICTIM; check to be sure they are breathing and airways are open (if not CPR is a must whether you suspect broken chest or rib bones.) Cover the patient with a jacket, blanket or your own body until help comes. Our own bodies generate heat. Talk to the victim and keep them awake (if it's possible) in case of concussion. If alone (this is dangerous) and for example someone is changing a tire and the car falls on their arm and is badly injured, the body goes into shock to protect itself. However, before jacking up the car off the victim's arm, and if possible (airways open and victim speaking) you should give them salt and water (at least 4 ounces) before removing the weight from their arm. This is a quick way to reduce severe shock until you can get the ambulance there or get them to a hospital. This method should only be used when there is no help for miles around or it will be a couple of hours before help comes. A tourniquet is used to stop the blood flow, but must be tightened and loosened every 10 - 15 minutes.