In instances where there's nowhere to bounce:
Expose for about 1/2 to 1 stop under the ambient. Make sure your shutter speed stays adequate for people - I'd suggest a minimum of 1/80 to 1/100. If you're having trouble keeping your shutter speed up, don't be afraid to increase your ISO. Sensor noise is almost always preferable to motion blur.
If you have ETTL metering, set it to FEC for proper exposure or perhaps +1/3 stop over proper exposure; if you don't have ETTL then you're going to have to do some trial-and-error with the first few subjects to get your flash power dialed in, then make sure you stay the same distance from your subjects for all future shots.
Warning: If your aperture is wide and your ISO is increased, direct flash may be too powerful even on the lowest power setting. In this case, point the flash away (or up or whatever) and use a bounce card to direct a small amount of light to the subject.
A flash bracket, to get the flash farther away from the lens axis, will help a lot. This will also allow you to keep the flash on top even when shooting in portrait mode.
Remember that you can bounce off more than just a white ceiling. A cream-colored wall, an assistant holding a reflector or a piece of white foamcore, or even a big fat guy in a white shirt.
If there's nowhere to bounce, the plastic snap-on "diffuser" cups such as the Sto-Fen Omnibouce will do nothing. No, scratch that, they will eat your batteries faster. Those diffusers "work" by scattering your flash all over the place and hoping there's something for the light to bounce off of, back onto your subject. If there's nowhere to bounce, all the scattered light is wasted, and you still only have a hard, small direct light source between your flash and the subject - except now there,s a crummy piece of plastic in the way.
On bounce cards:
The bounce card devices such as the Rogue Flashbender have the potential to work, because they make the effective light source larger. If you're somewhat close to the subject, this can make a noticeable but not huge difference. I hate the name "Flashbender" because you can't actually bend light; you can block it or redirect it but you can't bend it.
Last edited by nathancarter : 08-02-2013 at 08:32 AM.