The lines from the second and third point will cross at a certain point, and from this intersection, draw a vertical line down towards the angled lines coming from the bottom point. Repeat this step through the middle point and the same through the top point, but with the top point, mark out the angle downwards.
Draw a line back through the lowest point from the 30 degree angle on each side. Draw a horizontal line through the lowest point, and using the protractor, mark out a 30 degree angle up from the line on either side. Using the ruler, draw a vertical line on the page, and mark three equally spaced points along it. You will need a piece of paper, ruler, pencil and protractor (or for the shortcut version, using gridded paper, jump to the next section).
The most common isometric drawing is that of a cube, and drawing a cube using isometric projection is very easy. 3D shapes drawn with isometric drawing (Image credit: Cmglee)