How to troubleshoot a faulty starter motor on an Audi A4?

I have been having trouble starting my Audi A4 lately and suspect it might be a problem with the starter motor. What steps should I take to diagnose and fix this issue?

First, check the battery and make sure it is fully charged. If the battery is fine, then you can try cleaning the connections between the battery and the starter motor. If that doesn't work, then you may need to replace the starter motor itself.