Keep it to about a page, no more than 2. If education is thin, then highlight and emphasize your previous work experience, certifications, association memberships, or anything in your history that is related to the field/job for which you are applying. Volunteer work is still work experience. If you've taken ad-hoc classes and/or have experience in doing particular tasks, bring those to the readers attention. The resume is there to get put into a pile that the employer then says, "this is enough to make me want to interview the applicant and find out more about them". Also, if you have contacts/references within the industry who are willing to speak on your behalf (be sure to check with them before listing them), put down their name, where they work, what of your experience they will address, and multiple methods to contact them (phone and email is good).