In everything we do we can be a volunteer. It may be at work, the grocery store, or at home but in every moment you can be a volunteer. Your significant other may have had a bad day and you could volunteer to cook, do the dishes, or a multiple of things. Someone may say something in passing and it could be an opportunity to help them. Everywhere you look there are opportunities.
Pay attention to what people say, there is always an opportunity to volunteer to do something for them!