Wow, thank you in advance! We are always looking for volunteers from the community...esp. upper level Math. I would just contact the principals at the schools close to where you are moving. That's the way volunteering is handled, by the individual principals, not through the district offices. You'll have to get security clearance first, of course, but the principal(s) can help you with that. It's a 3 or 4page form you fill out, then your background is checked.
If you have some idea as to where you'll be living, you can PM me and I can give you the names of the nearest middle and high schools and tell you which ones might be in the most need of tutors.
Again, THANK YOU!!