Ensure accuracy. You'll need a tape measure, straight edge and graph paper.
Measure clockwise. Record the overall length of each wall, working to your right around the room. Label walls, windows and doors with numbers.
Get the width and height. Take horizontal measurements of walls at 36-inch height. Record vertical measurements floor to windowsill, from windowsill to top of window, from top of window to ceiling, then from floor to ceiling.
Find your center. Indicate the centerline of all permanent features in measurements including wall oven, range, sinks, windows, doors, closets, ducts and outlets.
Include the trim. When measuring doors and windows, the casing is considered part of the door or window. Measure from one side to the other of the door or window trim, then measure from the outside of the trim to the middle of the window or door.