Small employers hiring around Columbus - any advice?

A friend who works at a local manufacturer says there are openings not advertised online. I am in Columbus, in case local advice matters. One is a print shop, one is an accounting firm and one is a clinic. Should I visit in person?

Visiting in person worked for a trades job. For office jobs, email was better.

A short email with two sentences about what you can do and your résumé attached worked for me. I followed up after a week.