Decide on the scale you wish to have your plan. Architects and engineers, use different scales for their projects. A commercial scale may be an eighth-scale. Most residential plans are drawn to a quarter-scale. This means that each inch on the plan will be equivalent to four feet in real terms.
Research the symbols used to represent furniture, doors, windows, etc. This only matters if you are going to be using the plan in a professional context. If it is just for yourself, come up with your own symbols, just remember to keep a key for easy reference.
Begin with the outside walls. This will give you the plan for the overall building. Measure each wall in feet and divide by four, for which each block of four feet will be represented as an inch on the plan. Using a measuring stick, draw the lines on your graph paper. If you prefer, you can use a T-square to line up the corners.
Draw in the thickness of your walls. You should include any finishing that will be given to the outside walls such as shingles or rough walling.
Use your triangle and T-square to measure out the interior walls and mark them on your plan. You will use the same scale as the exterior walls. Treat each story of the building separately, marking above which level it is. This avoids the one plan becoming too cluttered.
Using the shell you have drawn mark the locations of furniture, doors, windows and electrical sockets. Be sure to measure them correctly and scale them down as before. Use the measuring stick to ensure that the distances are accurate.
Label everything. Mark all interior features with their name such as stairs. Mark the dimensions of all walls, windows and furniture, using the proper measurements. Do not use the scaled down versions.