Are you in US? All the reqs are state by state. For my Corps, to volunteer as an "observer" the minimum reqs are a CPR card and the ability to lift a stretcher. There is a simple application with a background check and interview. To drive you need a clean DMV abstract and a practical training exercise. To EMT you need an active EMT cert and 8 shifts as a "Crew Chief in Training". There are other specializations and training you can get.