I’ve been using the new-to-me Nikon SB-800 flash lately and I’m having to learn how to use a flash this strong. Using this flash for close-ups is like using an atom bomb to roast a weenie. When you were a kid did you ever burns ants with a magnifying glass? Used up close for head shots at full power that’s what this flash is like.
So I exaggerate a little, but for short-range people photography it’s occasionally blowing out the picture big time. Part of it is the flash’s power. The other part is that the SB-800 is a zoom flash. It zooms with the lens, shaping the light into a narrower beam for longer focal lengths.
I need to remember to carry the factory diffusion dome. It softens the light like all diffusers do, but on the SB-800 it does something else. The flash detects when the diffuser is attached and switches to wide angle (24mm), regardless of the focal length of the lens. If I forget the diffuser I need to go into the menus and turn off zoom mode for closeups.
I’m also getting in the habit of taking a picture, checking the LCD, and then adjusting the flash strength – usually downward.

What about using a bounce card with, or instead of, the dome?
I have a D 40 with the SB 600 flash. Granted, it’s not quite as strong as the 800, but is roughly comparable.
I have a diffuser (not a dome) on the flash and 90% of the time I also use a cardboard bounce card. I’m pleased with the results.
If I REALLY need the flash to carry I’ll shoot straight and sometimes take off the diffuser as well. That’s happened, but it’s unusual.
I thought I posted a comment here yesterday. Guess it didn’t take.
That’s a good point. I’m used to using a Sto-Fen diffuser on the SB-400, so I’m comfortable with that, but next time I’ll try shooting straight up and using the bounce card.