I guess technically I started when I started adopting, even though I did not concider it rescue back then.
When I actually started working in a rescue group: That would have been when I decided that adoption had to cease, but I still needed to help MORE CATS. I started to foster. Now not only do I foster,but I man the tables at adoption day events every other Sunday. And I've helped write some informational fliers to be handed out to hte public who'd needs to learn about "things". All voluntary.
Actually, thinking back, I did work (a paying job) at our areas first and largest no-kill shelter as kennel help before I began pet grooming, but the volunteering is so much more rewarding.