[header] How to write a letter asking to volunteer [title] Browse open volunteer positions. [step] These can usually be found on a company's website, either with the list of paid job openings or in a separate listing specifically for volunteer positions. [substeps] Look at multiple positions to find one that would fit you best. 
Get a sense of what the position you're interested in requires of its applicants. It's important to do this before applying, because even though it is not a paid position, there may still be a certain skill set, level of experience, or education background required for that position.