This is a technique I came up with to help with drawing people in perspective. The top part of these images is a basic grid drawn in perspective to hopefully help with drawing environments. The bottom part is a sideways view of the top image that includes the position and angle of the camera. The lines converging towards the camera lens at bottom correlate with the horizontal lines at the top.
You draw a rough, side view of the person you want to draw in front of the camera at the bottom, and use the lines converging towards the camera to figure out how to draw them on the image at the top.
If the top of the head is on the second line on the bottom image, then you draw the top of the head on the second line on the top image. If the bottom of the head is between the third and fourth line on the bottom image, then you draw the bottom of the head between the third and fourth line on the top image, and so forth.
Here is an example of what it looks like:
