I would check Facebook and websites from organizations you are interested in volunteering with. It would also be helpful to call to see if they are planning any events. Or, you can always start your own .
As Austin said you can check around school or just around town for poster and flyers. You can also check online I myself use meetup.com or you can try volunteering at places like animal shelters and meeting other people to do stuff with that way or you could always start you own group and doing your own events.
hey from what i have seen since i joined this is a very frendly place, so i dont think your going to get trolled .. and i would check around town for posters or flyers, or around school, thats probable the first place they would post info. about something where they need volenteers good luck