When you create an isometric drawing, "vertical" lines stay vertical, but "horizontal" lines are drawn at either 30 degrees or 150 degrees to give the impression of depth to the drawing. Here's an isometric "cube":
It has a 3D appearance, but really it's just 2D lines.
Now, you could do this by setting your polar tracking increment angle to 30, but that would let you snap to non-isometric angles like 60 and 120. You could also manually set individual polar tracking angles, but you'd have to take them off manually when you were done.
So instead, you can use the "Snap type" setting of the Snap and Grid tab of the Drafting Settings dialog box. (To find it, right-click on any status bar icon and choose "Settings".)
Set it to Grid, Isometric, and close the dialog. You don't have to turn on the grid or snap. Suddenly, your cursor changes. One of the axes is still vertical, but the other is aligned at a 150-degree angle, and it's changed colors.
When you turn Ortho on, you'll see that a "horizontal" line is now at 150 degrees instead of 0.
This curso mode is called "isoplane left". It's "left" because it's lined up with the left side of an isometric "cube". The other available isoplanes are "right" and "top". To switch between them, press F5.
With the help of isometric snap and ortho, you can quickly draw in any of the three isometric planes.
To get your regular, square cursor back again, change the snap type back to Rectangular.
Later this week, we'll draw some isometric circles, then add some dimensions to an isometric drawing.