A sharp pencil is essential for making accurate cuts. To keep the pencil point sharp, rub it back and forth a few times against a sanding sheet. This will give the pencil point a chisel shape which is excellent for marking.
A seller disclosure form can give you an idea of potential problems, but it should never be considered a substitute for a professional home inspection. Sellers may overlook problems, and often not be aware of them. It’s smart to use the disclosure as starting point, but hire a pro to get the whole story.