For this first "lesson," I'll just say a few simple things about composition, using this illustration for the title poem Gnomes of the Cheese Forest as an example.
All through middle school and high school I took drawing and painting classes with an amazing artist from Detroit named Nancy Prophit. She has since passed away, so it's my honor and privilege to share with you one of her many tips that's always stuck with me. Mrs. Prophit taught me that if you have several objects in a picture, particularly if it's a plural number of the same object, it's always best to group them in odd numbers. Avoid having too many even numbers of things in your picture, as this will make things look rigid and symmetrical. Odd numbers will appear more pleasing to the eye and more natural.
For example, in this illustration there are 5 "cheese trees", 7 gnomes, 3 goblets, and 5 rock "clusters" (meaning one rock or a larger/smaller rock grouped together).
Try to frame your background elements around your characters so they frame them in interesting ways, avoiding tangent lines and simply trying to find ways to make everything fit.
Anyway, I hope that helps! Happy Drawing!