I start with pencil and paper. If I find it's complex enough to require software I'll move to AutoCAD because I'm familiar with it through my work, but I find sketchup is easier to learn and would recommend that to anyone without prior modelling experience.
What software do you use to design a quick rendering to get your idea out of your head? (AutoCad, sketchup, etc)
Where am I?
In Strong Towns you can ask and answer questions and share your experience with others!
I have been doing this for over 40 years and my business is engineering so we are mostly AutoCad and Revit. My architectural and planning clients were originally AutoCad (not counting hand drawing) then went to Revit when it came out but now are using Sketchup in both large and small firms. I even have a carpentry contractor who is using it to do layouts and work out issues prior to construction. In my opinion, AutoCad and Revit have really become too expensive and too complicated for all but large and complicated projects. Hand drawing is often quicker, always less costly, but is a dying art.