Emphasis is about deciding what is most important in your artwork, that you want all viewers to see and appreciate. Every artwork needs one or more areas of emphasis, called focal points. Otherwise, there's nothing to look at. Artists create emphasis by creating focal points, and then designing the rest of the composition to lead our eyes to these focal points - a technique referred to as movement. I once heard an art teacher confuse movement with motion lines, that cartoonists often use. It's not the same thing. So, more principles:
1. The center of the picture is also the natural center of interest. It's where people typically expect to find something important.
2. Square, rectangular, & circular frames all lead our attention to the center of the picture. That's about 90% of all frames, but there are shaped canvases that can draw our attention elsewhere (see my lesson on choosing canvas shapes)
3. Smaller circles and squares inside a picture can focus attention to what's inside them, like a frame-within-a-frame. Think of halos. It doesn't have to be obvious, either. You can break up a halo and it still works, or simply put white around a focal point - something James Gurney calls "flagging".
4. Most artists don't want people getting stuck in the center, so they put the focal point outside of it. That way people feel free to look around the picture, at all the details.
5. as shapes get smaller, higher up, and lighter, they seem to be farther away. Shapes that are lower, bigger, and brighter seem closer to us. When objects are closer to us, they seem more important.
6. When one shape overlaps another, the one in front is more important, but both shapes join into a single visual unit. overlapping is important in realism because it looks more natural, especially in groups of figures.
7. Beware tangents when shapes just touch each other. It's hard to see which is in front of which so it looks awkward.
8. A simple way to make a focal point is to create an area of high contrast in your work. It can be a contrast in detail, realism, colour, value, etc. People notice differences immediately.
9. Another way to make a clear focal point is to remove unnecessary details and elements. Artist Howard Pyle said, "They will never shoot you for what you leave out of a picture."
10. Another technique is what James Gurney calls "spoke wheeling" like the spokes in a wheel that all point to the center. In a picture, you can do the same thing with lines radiating out from a focal point. Remember what I said about some lines being invisible but still important?
11. When you draw people, a great way to lead people's eyes is with the direction of each person's head. Viewers naturally look at faces first, and whatever your figures are looking at, we want to look at too.