I&#x27;ll say pen and paper for sketching too, for it is the fastest tool to use, no need to chase the object you&#x27;ll draw, or search for where to modify the font.  You think and you draw, the quickest possible.  But then I&#x27;d move it to a digital platform because there it&#x27;s easier to manipulate a schema that you already have.  Though up until this day I haven&#x27;t done that. However for emacs users there is the builtin artist mode and for others who don&#x27;t want to use emacs there&#x27;s a program that is capable of sketches and flow charts via a script input, but I don&#x27;t recall the name, sorry.<p>In general I usually jot down whatever comes to my mind and try to structure it all later, or on the way witg intervals. It&#x27;s hard to think in a schematic way. So I&#x27;ll have my notebook and pen, and write whatever comes to my mind <i>asynchronously</i>, that is I won&#x27;t wait for the next thought. If I&#x27;ll present my idea to someone else, I ll try to have at hand a schema and some notes both as brief and as clear as possible and I&#x27;ll skip details for not making premature commitments.