Here's a tip from the funny and talented children's author Ruth McNally Barshaw, creator of the popular and wonderful Ellie McDoodle series. I'm glad she suggested stick figures, for those of us who are less dextrous artists...it works!
"Sketch or draw the scene that isn't working, or the last scene that did work. It doesn't need to be a fancy illustration -- I often use stick figures and simple shapes. This always unblocks me (and it has a solid basis in Art Literacy studies: creating art first makes subsequent writing richer)." Ruth McNally Barshaw