Seems as though the biggest cause of engine failure in light aircraft is fuel starvation. Perhaps it is prudent then to quickly check fuel on/switch tank, mixture rich 1st. When well rehearsed this takes around 3 seconds. Then trim for best glide. Of course this works best when engine fails in the cruise/decent and may not be such a good technique when climbing as the speed may bleed off rather more quickly. Putting the carb heat on may be useful, but it is highly unlikely that carb ice will cause the engine to stop suddenly without any warning signs before hand.