Storyboard artist and animation historian Mark Kennedy on keeping a sketchbook:
I’ve seen artists on the Internet question the necessity for this, saying that you can’t really learn anything about drawing by carrying a sketchbook, and that the drawings you do in a sketchbook are always dashed off, careless and sloppy. […]
The real reason I carry a sketchbook is so that I can record and remember details that I observe. Drawing from real life is the best way to teach yourself how people look, act and move in a naturalistic way (and help you remember it later). Life drawing and studying the work of other artists and animators are great learning experiences, but those things aren’t the same as studying real life. A great life drawing is an amazing feat and you can learn a lot about drawing and anatomy by going to life drawing. But very few life drawings give you a lot of information about the model’s personality and what kind of human being they are. You’re never going to create an original story or character based on a life drawing model you saw.