Scott Knauss and I were trying to get two 580EX II flash heads to fire from a single STE-II controller. Due to the low angle of the sun, and the sailors of the N8 department wearing their dress blues, we needed a lot of light. So I spent entirely too much time fumbling with my flash trying to figure out how to set it as the "B" flash in a two flash group. All of the other times that Scott tripped the shutter to test the light I was holding the flash away from me, but as my luck would have it the one time I'm looking right into it it works. So what does the image demonstrate, other than I'm sometimes a dumb ass?
Know your gear.
Don't wait until your out in the field trying to setup for a shot to figure out how something works. Take the time to read the manual and practice at home, when mistakes won't cost you a once in a lifetime photo.
Don't be a dumb ass...