Writing a reference letter for a volunteer can be difficult. You want to avoid the cliches, yet give an insight into the person. Pub Med Central gives the example of a "fantasy letter" that describes the all-too common reference that tells the recipient that this person is the ideal candidate in every way. This can render the whole exercise meaningless. When an employer asks for a reference letter, it is because she wants learn more about the applicant by communicating with someone who knows him.
Know your candidate and the volunteering position she has applied for. Look back at records, or speak to colleagues to remind yourself of the candidate. Check the position she has applied for and plan your letter, accordingly. Write a factually correct letter. Avoid being formulaic and don't hesitate to offer an opinion based on your experience.
Introduce the letter by saying why you are writing. Write, for instance, "I am writing in response to your request for a reference for Jane Brown." Mention how long you have known her, and in what capacity. For example: "I employed Jane for three summer vacations at my store." Give concrete examples of her attributes, such as writing about a time when she worked late because a colleague had not turned up.
Ensure that the content of your letter is relevant for the position. The candidate's proficiency at science may not be particularly relevant, if he is applying to work at a center for the elderly. However, his ability to work well in a team will be crucial. Summarize your views of the candidate at the end of the letter. State that you think he is suitable for the volunteer position, if that is the case.
Remember that the candidate has applied for a volunteering position and this may require particular strengths. Some of these are interchangable with job skills, but not all. Mention if you have found the person cheerful and willing to help, and motivated by more than just money.