Tax agencies may be annoying to deal with, but the IRS has one of the best websites of any entity in the U.S. A client told me about the IRS’ Virtual Small-Business/Self-Employed Business Workshop. It’s an excellent resource on what you need to do to deal with tax agencies. It’s well organized, and it has a lot of useful information.
My client who told me about it said to me, “I wish I had seen this when I was first starting out.” The video has examples like keeping a written mileage log, and what you need to do with it. It’s well worth the time to watch it.