Isometric sketching allows you to draw simple three dimensional shapes that appear to be sitting on a table.
Here is a simple isometric worksheet you can download and try.
Here is an Isometric Dot Paper you can download and try. Each dot can represent 1/4 inch.
Here is an Isometric Grid Paper you can download and try. Each grid represents 1/4 inch.
Here are Four Isometric shapes you can draw. Each grid line represents 1/4 inch.
To see you someone else's explanation of Isometric Sketching, click on this link:
Below is a simple Isometric drawing of a block of wood.
As you can see, it is drawn with vertical lines and lines drawn at a 30-degree angle to the horizontal.

A good skill to develop is to be able to draw a simple cube on plain white paper, using only a ruler and a pencil. As you practice, you need to learn to hold the ruler at an approximate 30-degree angle as you sketch simple objects.
Isometric Sketch
The isometric projection is the basis for the typical three-dimensional engineering sketch. The three axes of the isometric sketch form mutual 120 degrees angles with each other (see example below). Alternatively, there is a left axis at 30 degrees upward from the horizontal, a right axis at 30 degrees upward from the horizontal, and a 90 degrees vertical axis. The proportions along each axis are in the ratio 1:1:1. The term Isometric means equal (iso) angles and length (metric). Circles on the isometric planes appear as ellipses in isometric sketches. Isometric grid paper is a convenient aid in sketching isometric drawings with both straight edges and circular features.