This isn't a tutorial page, but rather a general exploration of the elements and aesthetics that go into stereogram creation. For more of a tutorial, see Gary W. Priester's Stereogram Tutorial Page at: http://stereogram.i-us.com/
The main element all autostereograms have in common is a verticle element in one form or another. It is a combination of the repeat of this element with subtle differences that is the crux of the autostereogram 3-D effect.
This verticle element may be random dots, or a portrait of your significant other; contiguouis, or stacked; patterned, or not. Color is optional because those subtle difference are based on shape and form. Though verticle elements may be stacked on top of one another for diffent layers of effect, overlapping creates effects that must be delt with.
The Depth Image: