Our recruitment should motivate people to join our team. It should help stimulate interest and share how any and many can get involved. Be sure to have the necessary resources for your volunteers and your staff who will supervise and manage your volunteers. Include recognition. When the "thankless" job never produces any acknowledgement, you can expect a revolving door of volunteers coming and going until someone learns how to say or show a "Thank You" somehow.
I saved retention for last because what you do with the previous items helps you retain people. You don't retain people when you don't keep supplies on hand and you fail to recognize their effort. Retention is about relationships. What type of relationships have been developed with your staff, clients, other volunteers, and others? That will make a difference in whether you are able to keep people on board or not.