Again being very honest about what you “expect” of them and understanding what they expect of you and the role. Misunderstandings could lead to them becoming uninterested or not continuing.
Keeping busy, interested and engaged is crucial. If the work is interesting and they feel what they are doing is worthwhile and rewarding it will be a great incentive to keep going.
Recognising good work from you is essential too. Feedback is always good.
If you have a good interview, speaking to the Volunteer about their work history, hobbies, interests, likes & dislikes is the best way to match skill sets and personalities to the best opportunities.