Measure the dimensions of your rooms or home. Note the length and width of each room, and the external dimensions of the house, if necessary.
Assign a dimensional key to your drawing. This will depend on the structure's size. If you're only doing one room, one inch or one centimeter on paper to one life-sized foot is an adequate base. If your draft is for a home or apartment, you'll need to reduce the ratio to a quarter inch or less per foot.
Convert the dimensions you are drafting from the life-sized measurements using your key. A 12-foot by 18-foot room, using a half inch to one foot ration, would be drawn 6 inches by 9 inches on paper.
Mark the center of your paper by measuring the length and width, and making a mark at the midpoint of each length. Draw the outer dimensions based on this center point. Lay out your sheet of paper in landscape view on your work surface. Halve your longest dimension and measure out that number of inches right and left of the center point, making a tick mark at each end point. Draw a straight vertical line at each tick mark. Do the same with your shorter dimension, measuring half the number of inches above and below the center mark, and drawing a horizontal line.
Place rooms within the building's outline, if you're drafting a space with more than one room, closet or other enclosure. Begin placing rooms at the corners. Convert each room's dimensions, measure adjusted length and width off of the appropriate corner of your drawing, and make a tick mark at the measurement. Draw straight lines from each tick mark with your ruler till they intersect.
Measure the placement and length of doorways and windows. Note how far the doorway is from one corner in the room and the direction it opens -- into or out of the room. Convert these dimensions and measure the doorways on your floor plan, adding a tick mark at both sides of each doorway. On an angle from the wall, draw a straight line the width of the door from the hinged side. Draw a straight line perpendicular to the wall from the free edge of the door back to the wall. Measure out the windows on your floor plan and mark each window's edge with a tick mark. Darken the portion wall containing each window by drawing over it thickly two or three times with your pencil.
Draw a straight line outside of your draft's edges, a half inch to one inch from the outermost edge. It should be parallel to the top and right side of your room or building. If you have one room, simply write the life-sized length and width of the room next to each of these lines. If your floor plan includes multiple rooms, break the line up with tick marks and write the length and width of each room in the appropriate spot.