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The tutorial is for a 580ex but the principles can be applied to other flashes. The benefit to a 580ex is that it can be set up as a master or slave while the other canon flashes can only be set to slave.
With one flash, one of the best method is to bounce flash off of the ceiling. The surface that the light bounces off become the new light source. An alternative is to get an E-TTL cable (Canon OC-E3 or some other knock-off) to raise the flash higher than the lens axis. This will start casting shadows down to create a picture with more depth.
When I shoot flash, I shoot in M mode. I initially start with iso 100, f/5.6, and shutter speed at 1/125. If I want more of the background, I increase the iso, open up the aperture, and slow down the shutter speed to bring in more ambient light. You'll have to experiment to see what works best for your creative style.
When I used the flash for fill-light, I shoot in Av mode. I also decrease the flash power so that it doesn't overcome the ambient light.
I hope this info makes sense. If not, the website that I gave you will do a better job explaining.
Grab a white index card and a rubberband.
The 580ex has a built in white card. The purpose of the white card is to create sparkles in the subject's eyes. If you look in the 580ex manual, they call the card "catch-light card." The card doesn't soften the light or bounce much light. Combining bounce flash with a white card works well. The bounce light provides the soft light while the catchlight card creates sparkle in the eye. The card should be used when outdoors or if you don't have a wall to bounce the light off of. If there isn't a wall, most of the light will be lost going out towards space. The amount of bounce you get off of the card isn't significant enough to light up your subject to create a flattering image.