Test em on the ground.
Use em to taxi.
After takeoff, turn em off at safe height (after 500AGL).
Let your eyes adapt to night (usually 30 minutes).
Adjust instrument lights to suit (you'll find you can actually see outside - even when its really dark).
Use minimal legal external lighting (as mentioned before - less scatter).
Landing - really depends on special ops or runway approaches. (a height that suits usually by 300ft for runway)
The discussion could really be split into some different ops, such as CTA / Non CTA, VFR/IFR, and more importantly flight over buit up areas vs vast blackness with miminal ground lighting. Also add to that black hole (minimal ground lighting approaches) vs runway (well lit approaches).
It is going to vary greatly depending what your mission task is.
For me, I like to have just enough internal lighting to enable me to see the instruments and have some portion of night vision outside. So this would preclude using the landing light on permanately.
Fly safe.