First I created hundreds of abstract shapes in photosphop, corel painter, or alchemy (I recommend downloading the free program here: http://al.chemy.org/) You can also use paper and ink, marker, or paint.
Next I created hundreds of abstract linear designs using photoshop or corel painter. If you use photoshop try downloading and using a chalky or pencil brush. Again you can just work traditionally with paper and pencil.
The last technique was to find images with and abstract theme or design to them such as: carpet stains, clouds, wood, stone. The more you find the better.
Here are a few of my results:
Finally, I picked out the designs I liked the most or where the most out of my comfort zone and cleaned up the line work and then rendered them in photoshop in black and white. Perhaps at a later time I'll go back and render them better in color or do this exercise all over again.