Draw both curves on one set of axes

1. Put price on the vertical axis and quantity on the horizontal axis, using the same axes for both curves, as in 2.2.2 and 2.3.2.
2. Draw demand falling from top left to bottom right and label it D, then supply rising from bottom left to top right and label it S.
3. Use one quantity axis for both, because the whole point of the diagram is to compare the two quantities at the same price.

Mark the equilibrium where the curves cross

1. The crossing point is the only place on the diagram where quantity demanded equals quantity supplied.
2. Drop a dashed line down to the quantity axis and across to the price axis, then label them Pe and Qe.
3. Label the crossing point itself if the question asks you to refer to it later, since a labelled point is easier to write about.

Show a shortage or surplus off equilibrium

1. Draw a horizontal line at the price the question names, then read the quantity where it meets each curve.
2. Below equilibrium the demand quantity is the larger one, so mark the gap between the curves and label it excess demand.
3. Above equilibrium the supply quantity is the larger one, so the same gap is labelled excess supply.
4. Add an arrow on the price axis showing which way the price will move, because that is what the gap causes.

Show a shift as a second complete curve

1. Draw the new curve as a whole line roughly parallel to the original, label it D1 and D2 or S1 and S2, and add an arrow.
2. Mark the new crossing point and label the new price and quantity, since the shift is only worth drawing if its effect is visible.
3. Move one curve at a time unless the question says both have changed, because two shifts at once make the outcome ambiguous.