Use pencil, a ruler if you want and draw guidelines to help you. The drawing should fill the entire page. Refer to the previous post for examples of isometric drawings.
Isometric drawings: are 3D drawings. They show three sides, all in dimensional proportion, but none are shown as a true shape with 90 degree corners. All the vertical lines are drawn vertically but all horizontal lines are drawn at 30 degrees to the base line. Isometric is an easy method of drawing 3D images.
Check out this video of an isometric drawing of a chair.