Most engines shuoldnt be run up until the temperature is at least at the bottom of the green. However, in hot conditions, idling for too long can cause plug fouling. Taxiing is the same, if you require a lot of power to get moving, try to avoid doing so until the temps have at last started to rise and the pressure has stabilised. As was said, consult the POH/AFM, and there is also some good stuff from the engine manufacturers at their respective websites.
Kerms