Give inductions. In the event of a fire, you don't want volunteers mistaking the stationery cupboard for the emergency exit, so do a quick guide to health and safety. Familiarity with the set-up means fewer questions later.
Clarify their role. If you need volunteers with specialist skills, don't bank on them appearing on your doorstep one day, as if by magic. Advertise on your website and interview likely candidates.
Use the talent. Volunteers don't solely comprise feckless students and the terminally unemployable. Usually highly self-motivated, they will often have hidden skills or knowledge that could be of benefit to your organisation.
Make them welcome. Don't cast them adrift in a sea of uninterested faces. Introduce volunteers to the colleagues with whom they'll be working. A good experience of volunteering is good PR for your organisation.
Pay expenses. Volunteers are working for free, but this doesn't mean that they should be out of pocket. If you're worried about expense claims for a three-course pub lunch and a bottle of wine, set a flat rate - say £5 a day.
Give them feedback. A five-minute chat and a short appraisal of their contribution to your organisation give structure to their experience. You'd be surprised what you can learn from their views too. And stay in touch ...