This morning my demo was focused on one-point perspective. This little 20-minute demo of the iron truss bridge in the town of Clinton is a good example of simple, one-point perspective. To begin, I established the horizon line and vanishing point as part of the under painting. There are only three directions your structural lines can go in: vertical, horizontal or diagonal leading back to the vanishing point. If you remember this, you will get an accurate depiction of one-point perspective. Once the majority of my structural lines are blocked in, I can begin working on values, blocking them in from dark to light monochromatically in the underpainting.
Once this is done, I then began adding color, starting with the darkest darks and working through the middle value colors. For the brightest brights, I tried to maintain a balance of warm and cools, using the cooler tones for the snow in the distance and the warmer tones for the sunlit snow in the foreground.
Little exercises like this are great for understanding perspective. Try sketching these types of scenes on location in charcoal to really see how perspective translates depth and space onto the 2 dimensional surface of your paper or canvas.