Image from Artists Network
What is a Block-In? Haas explains that "A block-In is a light sketch of your whole composition before any details or shading are done to make sure it’s placed correctly on the page and that the proportions and distances are accurate."
The author says, "When drawing a face, students start with the eye; when drawing a flower, they start with a petal. They inevitably get the proportion and scale wrong or run out of room on the paper because they’re working from small to large." I'll admit it - I've made this mistake.
Read the complete article for more tips on developing a Block-In for your next art work.