how often are they changing or at least monitoring where their white balance is (or how it's set)?
ALL depends on what you're shooting and where you're shooting.
During formals I preset my WB and since lights are 95% consistent and I usually take 2 of same poses (unless its a large family group then 5shots should be enough) WB isn't an issue.
Once I go on-camera flash, again depends on what I'm doing and when, chances are WB will stay the same - the primary light source is the flash and same color consistency will be for most part of the day/evening.
Metering - again depends on what: for formals to setup a ratio and can either eyeball it (from experience) or meter it.
If the shot is underexposed, then my Caucasian faces will be redish.
Leave it in 'Auto', shoot in RAW, and correct to the dress/tux in post as req'd.
I shoot mostly JPGs unless I feel that I'll be in the environment where WB or exposure might be of an issue and time is essential - will switch to RAW. The more accurately I prep for specific shoot (wedding, in-studio portraits, etc) the less time I'll spend
correcting the images. I'll rather process them, then correct them. Difference being (add contrast, filter, etc - processing) vs correcting (grossly under/over exposed image, blue bride's dress that should be white, etc etc).
If you have anything more specific, and want to, feel free to PM me.