I simply contacted the director of parks in our home county. He put me in contact with the county parks volunteer coordinator. The rest is history, as they say. In our case the demands are few. Answer questions on registration (which is intended to be self registration), sell firewood, check the campsites for residual trash after a camper leaves, check the facilities now and then, and generally just provide a presence. If anything needs repair or cleanup we are to call park staff, this includes the restrooms. If anything needs enforcement, we are to call the ranger or the police, as we feel appropriate. Thankfully I've only felt I had to call the ranger once and the police never. It is stressed that we are NOT enforcement, leave that up to the ranger or the police.
We are provided a very nice full hookup site at no charge. In fact, in our county parks the camp host sites are the only ones with water and sewer.
In our case we looked to kill two birds, so to speak, by volunteering. One, we sold the house before Peggy was retired and needed a place to park our "retirement home". Second, we felt it would look good on our resume when/if we wanted to do this again elsewhere. It's turned out to be fun too, just the icing on the cake.
Jay & Peggy Monroe with Dolly
Can't take it with you - don't plan on leaving any behind
2016 Newmar London Aire 4553, Spartan chassis
Wrangler Unlimited toad