Small employers hiring around Detroit - what worked for you?

A friend who works at a local manufacturer says there are openings not advertised online. It has been weighing on me all week. One is a print shop, one is an accounting firm and one is a clinic. What do you write in a cold email?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.