I finished the picture book story I began last weekend!
First, I told the story with thumbnail sketches. Then I wrote out the text for each scene (page), asking myself the questions: what does my character want; what are his obstacles; what are his emotions; and how does he overcome the obstacle -- if he does at all in that particular scene. Then, it was just a matter of putting text with the pictures. Each question was not answered with words. Some questions — particularly emotions — were answered through the pictures.
I know it's probably unwise to send this story out to an agent before sharing it with my critique group, and definitely before completing several rewrites, but I'm going to send it anyway — we won't meet until next week, and I want to send this package out before then. In fact, I'm sending out everything — all 5 manuscripts written this year — in whatever stage it's in. If the stories are terrible, and if she's not interested in taking me on, I'm sure she'll tell me. And if that happens...well, I just won't do that again when approaching the next agent.