proportions

The lessons are from 7-10PM and at around 9:25PM our instructor started with proportions.

Take a pencil, hold it straight out in front of you, hold it either vertically or horizontally, depending on what you are measuring
close one eye and put your thumb on the not sharp end of the pencil and look at what you are to be drawing
now drag your thumb down or along the edge of the pencil until the distance between the end of the pencil and your thumbnail measure what you are looking at
This is the base measure
Using the base measure, measure how many base measures it takes to span the perpendicular direction of the thing being drawn. Once you have that number, now you know the proportion to use.

The example we did was to put a wine bottle on a table. Using the pencil horizontally, measure the width of the wide part of the bottom, then turn the pencil vertically, keeping the thumb in the same spot on the pencil, and see how many of those equal measures it takes for the length of the bottle. We went around the class and most of us had a proportion of a little bit more than three - ie, the bottle is a little bit more than three times as tall as it is wide.

The next part of the instruction was to then draw the wine bottle, but to make it fill whatever space you had available on the paper. The idea is to use the proportions to gauge how large to draw the base in order to get the height of the bottle to fit nicely in the space available.