Consider the lighting, ventilation, room access, electrical outlets and pipes you'll need in the room.
Draw the existing space as is and the design you want to create out of it.
Include new walls, doors, windows, electrical outlets, plumbing features and ventilation in your plan.
Mark the location of walls on the ceiling beams. You may need to remove a section of the ceiling to locate them.
Measure the framing for the walls. Include spaces for the doors and windows and determine where electrical and plumbing fixtures will be.
Lay out all of the cut frame pieces and mark them for the stud locations.
Attach the frames together, lift the frames and attach them to the studs.
Secure the walls in place. Use a level to make sure the frame is straight.
Place the new plumbing and electrical fixtures in the new walls.
Repeat the process with all of the remaining walls.
Add drywall or paneling to the walls.
Put in the doors and windows.
Paint the room.