Collect ideas based on what appeals to the target audience -- picture book publishers and young readers. Do your research. After you have written your story and before you begin illustrating, ensure that you read as many children’s picture books as possible. Visit the children's section of your local bookstores and libraries for a wide variety of picture books. If you intend to illustrate children’s picture books for specific publishers, look for guidelines on their websites and make sure you follow them strictly and carefully before you submit.
Focus on the main theme and tone of your book. Your story’s plot and mood will influence and help establish the style of the illustrations that you will later create. For example, a slightly more serious picture book may contain images of darker colors or black and white sketches, whereas a funny story will most likely be illustrated with bright, happy colors. Keep in mind that the latter style is often more attractive to children and more appealing to parents who will often make the purchase.
Read the book’s text carefully. Divide the story into small parts. Each of these sections will require an illustration. Look for verbs that describe an action and try to separate the writing in a way that every illustration is attached to one of these verbs.
Create the first sketches for your final illustrations. Use your sketchbook to plan the book’s general layout. See how the illustrations fit on each page, alter the pictures’ sizes and make sure they are easily understood. Simplicity generally works better for children, although detail and richness in color achieve a more striking visual impact.
Colorize your illustrations. Use programs like Photoshop or Microsoft Paint to illustrate your picture book in a digital format, or draw sketches and color them by hand. If you do it by hand, then select between watercolor images on paper or bright acrylic images on canvas. Go for energetic oil paintings on canvas if you want to achieve powerful images. Work with various mediums and experiment with colors until you find the ones that are most suitable for your book.
Transfer any rough drafts to canvas, watercolor paper or an illustration board. Develop your drawings further further, scan them and either leave print them. Leave them in black and white if you want to save money, or color them vividly if the cost is not an issue. Bright and colorful illustrations usually attract a child’s attention more successfully. Attach the printed images to the corresponding text as a final step before submission.