Good advice Chris and agree with everything, but it should be added that exposure method really depends on the camera sensor.Chris S. wrote:.......
3) Turn your flash units on, set them to manual, and set up whatever triggers you use. Adjust flash intensity by taking pictures and examining the histogram (apply the ETTR method).....--Chris S.
ETTR is no longer needed with new cameras.
The ETTR method will improve shadow noise with older Nikons, most Canon, and Nikon D5, or D4.
Underexposing or ETTL with most, not all, new cameras, Nikon D500, D850, D810, D7200, Sony A7R, A7RII, A7RIII, Sony A6300 is the better method. The sensors on these cameras are ISO-Invariant so its safe to underexpose 0.3 to 0.7 all the time with any increase in shadow noise or DR penalty.
When I give tech presentations I show two slides taken of the same scene with the same shutter speed and aperture with D500 at ISO 400 and ISO 1600. One of these has to be darkened in Photoshop to match the other but the noise is identical.
All the best,