One of my most valuable assets is my sketch collection. This collection of sketchbooks contains pretty much all of the projects we have worked on over the last sixteen years plus all of the ideas that never made it past the idea stage. Rather than draw on loose paper which can easily be scattered or lost I instead do all of my idea sketching in blank books. Through the years I've filled more than fifty of the black hard cover books with many more new ones on the go. They are stashed everywhere. A couple are beside my recliner, another in my bedside table, a couple are in our vehicles and others wait on my desk for when inspiration strikes. The drawings that overflow inside are done with my favorite rollerball pen or whatever happens to be handy. Most of the drawings are loose and quick, capturing my creative thoughts and ideas while they flow. Often subsequent pages are filled with iterations of the ideas that morph as they are developed.
Once I've worked out a clear idea of all the details I can then do a more finished drawing which then is redrawn one last time for presentation.