My friend Tina Nichols Coury, author of Hanging Off Jefferson's Nose, did a series of short videos of children's book authors and illustrators giving advice based on their own experience. She interviewed me several years ago at the annual Breakfast With the Authors in Santa Barbara. My tip for the day boiled down to this:
If you are an writer/illustrator and illustrating your own book, make sure you don’t write something that you can’t illustrate. In other words, think of the actions that move the story forward as you write. The beauty of being an author/illustrator is that if you discover a section that doesn't work with the illustrations, you have the option of rewriting the text to improve the flow.
You can see the whole video by clicking here: https://www.youtube.com/watch?v=zoGAcBDVA0g