Diodes & Caps

My thanks to Mo for the discussion of pull up (and pull down) resistors
which has helped me in my troubleshooting. I'd like to ask (this would
be a FAQ, I'm sure) about the Diodes and Caps suggested in the stepper
motor coil wiring. Values, placement, theory? I thought these windings
had a bi-directional current flow, by their basic nature. The Crafter
controller I have has a bleed resistor across the supply capacitors, but
no diodes, as far as I can tell. When I run 5 Amps through my Camtronics
driver, this will become a critical issue, I'm sure.

Also note: I've seen http://eio.com/public/stepper/ before, but somehow
I just found http://www.eio.com/stepindx.htm
See also: http://www.euclidres.com/apps/stepper_motor/stepper.html