Use a notebook to record one character, one motion idea and one observation after every experiment. Dates and rough sketches are enough; the journal is for noticing change, not grading artwork.
Try this
Return to a previous entry after a few weeks and try its idea again. Describe what changed in the drawing, the movement or your own preference.
Take it further
Try adding a tiny thumbnail beside each note instead of writing a long explanation. If you work with others, agree on what can be shared; a journal can remain private even when the finished character is public.
