Where do the words go? When you have all kinds of characters, props and background in mind, this could be a very boring question. But the layout for text and pictures together will determine the entire look of the book spread. If there is no natural place for the words, it may look like the art is completed and could become hard to work with. They may cover a key face, conflict with a texture or get pushed to a corner that was left out of the plan.
You might not think that this part of the book has a lot of art in it, so you can ignore it. But this space is an important part of the composition. The blank space next to a character can help establish the scene more clearly. The space behind the text can help it feel more a part of the book by giving it a softer background form. The space on the margin can keep the whole spread from being too crowded. Planning ahead for text can make art and words feel like they belong together instead of having to compete for a spot on the page.
Take a short passage of text and create one full page spread rectangle. Before you start working in the scene, make very light marks to try out some basic layouts for where you can put words. Try one option on the left side, one option with words placed high above the character, and another option with text in a clear spot of the background. The marks should be loose, not final words yet. You are not doing actual typography, but you are getting a feeling for how the reader will take in the words and picture and the whole book spread.
A common issue is that beginning artists usually plan for text in the end after they have already thought out a character pose and background and props or colors. At that point they can not come up with a good spot for the words, and they are forced to cover something important in their picture or put a paragraph in a difficult position. Planning a text area in your sketch stage can help you avoid the above problems, and can help you think about just how much detail the page needs.
Try squinting at the rough sketch. The text area should still look fairly calm and empty if you squint. If it is covered with many strong lines or dark values or small bits, the words will not read well. To help it you could move a prop, change contrast values, simplify the texture or give a figure more space. The goal here is not a simple page, but controlling how much focus the reader puts on it.
Artwork and text can also control how fast or slow a page feels. A page with a clear area can feel slow. A page with a big figure around a small block of text might feel faster. A character that looks towards text can lead readers gently from one page to the next, and so can the position of text as you turn pages to the next one. Small details such as this can change the way the pages feel in the hands of the reader.
Before going from rough to cleaner drawing, ask if the words have their own place on the page. Check the space on the margins or around focal points like face, or busy spots on the background. If you can comfortably place words without taking away from an important part, then you can feel better about your work. A book that looks great will also feel comfortable to read, and the artist will be happy to put words to the story.