Isometric drawings are designed to show a three dimensional view of an object. The width and depth are both drawn at 30 degree angles.
The following guide will present to you the ways to create an isometric drawing.
You can use a picture of a Three-View drawing to get the dimensions. Using those dimensions you can make a isometric drawing.
Start with the front view and draw the construction lines that you would see from the front view. Make sure you draw these lines back at a 30 degree angle to the left. These would be light lines that overlap that give you an idea of what the drawing would look like. This is not the actual drawing of the object.
Then draw all the depth lines at a 30 degree angle back to the right. Connect all the lines that would be on the top view that you can now see in the isometric.
Now, once you have all the construction lines done, go over and darken the lines that should be the visible lines, the outline of the object. You have to think in 3D to do this. There are not going to be any hidden lines on an isometric drawing.
For a finished example of a isometric drawing (file viewable in AutoCAD LT), you may click the link below: