Start with the purpose of the plan
Are you recording an existing building, considering a new arrangement, or exploring a new building concept? For an existing space, record its measurements and fixed features first. For a concept, label assumptions clearly so nobody mistakes an early idea for a measured survey.
List the rooms and their relationships
Write down the spaces you need and which ones should connect. For example, consider the route from the entrance to the kitchen, or how guests reach a bathroom. Think about noise and privacy as well as proximity: a quiet workspace may need separation from a busy shared room.
Identify what cannot easily move
Mark structural elements, stairs and fixed services where you know their positions. If you do not know whether something can move, flag it as a question rather than building the design around an assumption. Changes to a building may require professional advice and approvals.
Think through everyday movement
Walk through the proposed layout in your imagination. Consider carrying shopping, opening doors and reaching storage. Measure the furniture you intend to use and account for the space needed to operate it. A furniture footprint alone does not include the room needed to pull out a chair or open a cupboard.
Compare a small number of ideas
Keep an initial layout and make a few deliberate alternatives. Change one major relationship at a time so you can explain why an option works better. Review each idea against the same brief, instead of choosing only the most attractive image.
Prepare for the free planner
Keep your room list, measurements and open questions together. The upcoming FreeFloorplan3D software will provide a place to create 2D and 3D building floorplans and download images for free. Until it launches, use the measurement checklist to prepare a clear starting point.