Besides, every drawing trick I know is really simple! Anyway, all this topic involves is looking at shapes and objects that repeat in your composition to give the feeling of depth.
The most obvious examples are the typical ones: telephone poles and railroad tracks.
We know each telephone pole (and railroad tie) is the same size, so as they get further away from us and get smaller, we perceive depth and distance.
This are obvious examples, but you can use that same trick - of objects repeating within your composition - to suggest perspective and distance.
Here, using the foreground, middle ground, and background idea I talked about in an earlier post, I created some depth in these incredibly simple sketches. In a city scene, you can use windows on buildings (which the viewer assumes are all roughly the same size) to create depth with just a few quick lines. As the windows get smaller on each successive level, that feeling of space going back into the frame is achieved.
Here, I drew a simple highway going over three hills. The road signs and lines on the road give you a sense of depth.
And almost every environment has objects that repeat that can be used to achieve perspective. Most city scenes are especially easy because there are always cars and people that populate the streets. But there are many other options too. Mailboxes, streetlights, sidewalk squares, billboards, etc.
This one by Franquin has cars and people to indicate depth, but he also uses the road texture, building windows, etc. My favorite touch is the vertical "Quick" sign in the foreground. There's a similar vertical sign in the background that says "Monopol" and your eye assumes that they're about the same size, because they're similar signs. Immediately, a nice easy sense of depth is created.
Another one of my favorite examples by Franquin. This time, he achieves a good feeling of depth by having close up leaves in the foreground, semi-distinct leaves in the middle ground and then suggestions of tree foliage in the background. Three different layers of leaves at different distances from the viewer, getting smaller and smaller as they get farther away from us creates a great feeling of depth and space.
The variations are limitless, and don't have to be obvious at all. Here, John Romita Jr. uses a statue in the foreground and similar statues in the background (on the top of a cathedral) to show scale. We assume all the statues are the same size.
Some more examples. From Cosey:
By Bill Peet, from his Autobiography:
Anyway, keep your eyes open for unique ways to use this technique in your own work. It's a handy trick for creating depth and perspective without it drawing attention to itself and distracting from the rest of the image (which can happen if you try to put telephone poles and railroad tracks in every frame). Here are some real world examples for inspiration.