[MaysonL]

Code review. Even if you don't have someone to review it, you can pretend to explain it to someone else, a line at a time.

Error logging. When you make a mistake, and find it, document it, with as much of the reason why you made the mistake as you understand. Keep a diary of these for a few months, and you'll be surprised by how much you learn, as well as learning which mistakes you're most prone to.