How to troubleshoot a faulty starter on a 1992 Audi 80?

My 1992 Audi 80 is having trouble starting and I suspect the starter might be the issue. How can I troubleshoot and confirm this problem?

The first step is to check the battery voltage and connections. Low voltage or loose connections can also cause starting issues. If those are fine, then try tapping the starter with a wrench while someone else turns the key. If the engine starts, it's likely a bad starter and should be replaced.