centaurus,
There is no magic in 400ft AGL - which is why I said rule of thumb. I used to fly 747 Classics, thus the flight engineer watched and trimmed the power during the initial climb. I did not handle the thrust levers until I needed to either adjust the ROC or level out at an intermediate altitude on the departure. I only suggested 400ft because tdracer suggested it.
I am really amazed this thread has generated so much comment. My only hard and fast rule was to take my hands off at V1, partly because it was an SOP but mainly, as tdracer has said, to avoid any 'startle effect'. Otherwise I handled the thrust levers as required - it really doesn't need an SOP - just do what is necessary!
When using autothrottle I always rested my hands lightly on the trust levers so that I maintained the tactile feedback of what the automatics were doing.