I volunteered at the 2018 Security Conference and ISC2 will send out a request asking for volunteers 4-5 months (I seem to recall) before the conference. Once they request members to volunteer there will be a series of steps to become a volunteer.
Hope this helps.
Dr. Warren Mack, CISSP
To make sure and get your name on the list as interested please email email@example.com. Then probably around April (ISC)2 will start sending out emails for people that are interested in volunteering.
If there are any questions I can answer regarding volunteering please don't hesitate to reach out. I have volunteered the last 2 years and am planning to volunteer again this year in Orlando.