Thanks I'm learning a lot here!
When to use 3200K and when 5600?
3200K: with Tungsten light (Note: I like to set it around 2500K-2800K with little tweak in WB Shift)
5600K: with Daylight
there are some other cases that you can use such as:
1. set your camera in ai servo
2. frame entire white paper or gray card (do not care about closing focus requirement since you are in ai servo)
3. take a shot of that white paper
4. perform your setting on custom white balance with an image that you have just taken
note: i do not use video; therefore, i cannot say further about it. but i use manual white balance for studying purpose only. in real shooting, i am using auto white balance since i can adjust it later (scott kelby already said, "there is no such unique standard requirement on using white balance, just use it to your taste"... might be i have just put my words into his mouth, but he did say something like that.) and keep in mind that you if you are shooting in different light situation (i.e. keep changing one location to another, close to television, computer, etc... manual white balance would not be prefered since you will probably have a hard time to deal with.)
me, not a prof. photographer, i am still in every day learning curve since i have started loving photography