A few years ago I used SketchUp to model some house extensions, was pretty useful to model window sunlight and shadowing through the year, and double check draft plans from the builder in terms of layout. It seems to have gone web-only now though, instead of an unpaid desktop program.

Seconded, that's what we used for our office.

Sketching (2D/3D) with pencil and paper for rough ideas.

As soon as any accuracy is needed, AutoCAD for 2D and/or Blender for 3D. Blender is usually enough, but I'm faster in AutoCAD.

If possible, I try to physically experience the new space or object, using my imagination and any props at hand. For example, I might put masking tape on the floor, following the layout of the drawing, and walk around them pretending they are obstacles.

I have used Sweet Home 3D and it’s great

http://www.sweethome3d.com/

A pencil, a ruler and graph paper.

Tech is usually way more cumbersome to use.

interested in how home network in wall