On the Saturday before the Rotary International Convention, District 9800 hosted The Big Difference: a day to pack 100,000 meals in FORaMEAL emergency relief food packs to send to people in need worldwide. 
Over a thousand volunteers packed meals on the day; most of whom had had nothing to do with Rotary, and many had never done a “volunteering thing” before. This is the purest and simplest form of volunteerism. Every package prepared is enough for a household of people to enjoy a warm, nutritious meal at a very dark time. And each volunteer had the chance to prepare dozens or hundreds of meals!
And why didn’t I pack a single meal? I worked as an MC, helping supervisors sort various problems, ad hoc volunteer training, moving supplies and finished boxes, coordinating groups in the setup, talking with members of the public about our work, and generally supporting the organizers with whatever needed doing.
Humans are social animals. Our brains are wired to reward us for helping other people. We all know this; it's why we all do what we do. Every Rotary member has had that “aha”! moment when they felt the joy of service. One of the best things we can do is share that experience with others.