As mentioned below, EMT or other first aid training is optimal. If training is not feasible though then in addition to the resources listed below, a EMT/paramedic textbook can be a useful reference and can be bought from Amazon. Nancy Caroline’s “Emergency Care in the Streets” is a classic. Emergency Care and Transportstion of the Sick and Injured by the American Academy of Orthopedic Surgeons is another quality text. These go beyond just first aid and discuss emergency scene safety, vehicle extrication, communications and operational issues, anatomy, physiology and pharmacology and other topics. Good reference material and also a good way to learn about how EMS services approach things. I suggest looking at the contents of different textbooks using Amazon’s “look inside” feature to find one that offer the content most relevant to your interests.