After spending quite a lot of time learning 3ds Max, SketchUp, Rhino and Maya, I decided that for me, personally, the easiest and most suitable way to visualise a project is freehand. If you can imagine and see 3d in your head, you don't need to always rely on 3D programs.

And drawing is so much FUN that way. 

PS: Modelling it with your hand- even better :)