One of the best ways that I have found volunteers is through the friends of other volunteers. The obvious starting point is to make sure that your volunteers have positive experiences, know their opinions are valued, and feel appreciated. The next step is to encourage them to bring their friends along.
Incentives are a fun way to get your volunteers thinking about who to invite. A coupon to your organizations gift shop or a participating store in town is always fun. I’m sure that a restaurant or store in your area would be willing to supply some 10-20% off coupons for a few volunteers at your organization. The publicity and extra traffic is a good trade off.
If you can offer incentives within your organization, that is all the better.
Of course one essential part of the incentive program is developing a simple spread sheet to keep track of who’s done what. You could lose a volunteer if he/she feels slighted by you. Be careful to stick to the guidelines you establish for the incentive program, and make sure that you deliver the goods as soon as possible. That will get people talking about the incentives and will hopefully encourage others to participate.