Determine the scale you're going to use. If you're sketching the layout for a very large room, you should assign a large measurement to each square, such as 5 square feet. If the room is smaller, assign a smaller figure to each square, such as 1 square foot.
Measure the room in question and translate it to paper. For example, if the room is 10 feet long and 12 feet wide and each square represents 1 square foot, draw a square on grid paper that is 10 squares long and 12 squares wide.
Measure the furniture you're going to place in the room, then draw it to scale on the grid. In our example, if you want to place a desk in the room that is 4 feet long and 2 feet wide, draw a square on the grid that is four squares long and two squares wide. Repeat with the rest of the furniture.