This is how I like to prepare a pattern for making a muslin and fitting. White kraft paper or banner paper got from the office supply, copying only stitching lines and other details (NOT SEAM ALLOWANCES!).
Other people do it other ways, but in fitting classes I teach, this is how I like it done. It's far easier for me to see alterations that go to stitching lines, as well as making sure seam lengths are correct after a pattern has been adjusted.