Finding a good fit for post retirement volunteer options?

I read in another thread that one retiree felt that her volunteer activities
were a key component in her staying healthy. It made me wonder how
do folks find the right volunteer position?

I'm in my late 40s and have a bit of time before I retire. I work very long
days and have a large property I maintain largely myself. Translate
this to I don't really have much time to explore volunteer activities now.
I do volunteer work with a few of the gardening societies but that's it.

For those who do volunteer in retirement, how did you find the right
fit for your interests, skills and temperament?

Tam