Upload & Sell: Off
My approach is to decide the approximate aperture/DOF to use first -- this is usually around f5.6-8 for portraits, more for products. Then using a light meter, I will adjust the main light's power until I get the desired f-stop.
From there I decide what are the roles of the other lights (if any, such as fill, hair light, rim light, etc), and decide what power to use based on the ratio against the main light (e.g. I usually go for 1-stop difference for rim light, maybe 1-3 stops for fill depending on how soft/hard I want the shadows, etc), and use the light meter adjust the power to achieve that desired f-stop.
Finally a take one final, combined light meter reading to determine the overall exposure, and see if I want to fine tune any further.
It sounds like a lot of work, but actually I use a bunch of Canon 600EX-RT speedlights with the ST-E3-RT transmitter so I can easily enable/disable flash groups and manually set power on each group with the transmitter; all the while sitting at the subject's position to take the light meter reading.