Rule 1. Turn every other program off.. .Rule 2. Once you start NEVER interrupt.. .Rule 3. Put any file names down on paper first, no way to go back to check.. .Rule 4. If indoubt, ask.. .Rule 5. If in further doubt, print out and ask an expert to do it for you. They might ask a $2-30 bucks, but it's worth it.
I always do my own, but I have a couple of spares at $60 USA sitting in a cupboard.