I kind of agree with you about showing up unannounced. How did you find out the barn is needing volunteers....did they specify how they would like to be contacted? If not, I would at least call first. If you do call, be ready to give them any info they may ask for. If you opt for the email, I would include experience if it will help...but if you don't have a lot of experience, I wouldn't say anything about it until they ask. When you do go in for an interview, I would treat it just like a paying job interview....bring your Id, have some references in mind (along with their phone #) and don't be afraid to talk yourself up. Good Luck!!!!