I switch off the headlamps; but parking lights on. About switching off the engine, I don't do it as AC won't be effective if the engine is turned off. Also, another concern at the signals are that the vehicles keep moving slowly, finding their way inch by inch. If I switch off the engine to a halt, then the drivers from behind start yelling at those who are in front of (that would be me, of course!) them. So, I let the engine idle.
I turn off the engine of my bike at the signal as it saves petrol for me & also saves the battery life, since my headlight, tail lamp, indicators, Pilot lamps & horns are all dependent on the battery. However Sometimes I can't help it & I always wish it would be better if there were timers to let us know how long before the signal will change. This is there only at few junctions like Liberty X road. I guess this small piece of equipment will go a long way in saving lot of fuel