This never replaces modelling things, or making mock ups in cheap simple materials but these come after the design work has been done on paper.
After all Paper and pencil are cheap.
Step 1: Sketching
In general for most people sketching flat is easier and will do.
A side view, a top view and a front view will show you all round your design
If you can manage it, then a 3D view, (called isometric view,) will give most none engineering people a better idea of your object