RE: The first start of the day
I must err farther on the side of caution with my engines because whenever I start mine up they're always rich. If its colder out than when I last ran the specific engine, I'll richen the needle 1/2 turn before first firing it off. If about the same air temp, I leave it alone until the engine warms up.
I use ambient air temp as the judgement factor as to how the engine is going to run from dead cold.
Thats just me though..