How to properly use a Nikon SB 900 speedlight for like outdoor portraits?

How do you properly use a Nikon SB 900 speedlight for like outdoor portraits?

Well personally, I like to underexpose the ambient by a stop or so & then use the flsh to light my subject to the required level.

That way you get richer colours in the background, your subject is still correctly exposed and you get a nice cathclight in the eye.

I tend to use flash & camera both on manual settings (not TTL) as I like to have control over the exposure and TTL (auto flash exposure) often gets it wrong.

Main use like outdoors would be for like fill in. On a bright sunny day a tiny "blip" of flash is used to reduce harsh shadows on the face. An alternative would be to use a reflector.

Aperture priority. Shutter speed chosen to accurately or slightly underexpose the ambient light. Set aperture to achieve the desired depth of field. If the chosen f/stop requires a shutter speed higher than the sync speed to expose the ambient light the way you want/need to, then you can use a polarizer to lower the shutter speed by two stops, or just use the appropriate type of and filter. Your SB900 and camera combo may also have high-speed sync technology so that you can sync the shutter at any speed.