First of all, my advice is worth exactly what you paid for it. So, I highly recommend going on a good first aid course. If its children you are interested in, then look for the 12-hour Paediatric course. But remember the syllabus we teach on those courses is aimed at professional help arriving within the “Golden Hour”. Most of the skills are transferable to a longer wait, so you could say to the trainer I often go walking in the hills how would I change this, rather than I am a prepper and the SHTF.
The foundation of all first aid is A - Airway, B - Breathing, C – Circulation. Everything is an airway, breathing or circulatory problem. So, for example, drink hot water it effects the airway, which swells and stops breathing. Spill the hot water on your arm, the airway and breathing are unaffected, but the blisters and shock effect the circulatory problem.
Use D.O.T.S to assess for a fracture. Deformity, Open fracture, Tenderness (or pain) Swelling.
Treatment for fractures is relatively simple, it does not matter if it is the neck, or the little finger keep it still. How you do that is the difficult part. I do like simple splints like the SAM or cardboard for arms, legs and joints. For a neck it is hold their head still and wait on an ambulance.
Broken bones are of course a circulatory problem, trapped blood vessels, bleeding and shock. But a damaged neck could affect the brains ability to control the diaphragm and lungs (breathing problem).
Remember the above is a very simplified version of what we teach, and yes I do teach first aid as a living, that I have typed out over a coffee and not as in depth as you will get on a course.