Ok as soon as you turn the key and the ignition lights come on the sensors are feeding information back to the e.c.u,outside air temp,water/coolant temp etc.The colder it is the longer it will need to be on increased idle(the modern equivalent of a choke)hence more fuel being injected,sometimes if it dumps a little too much fuel in it saturates the end of the spark plugs with fuel.As soon as its flooded every start attempt adds to the problem as more fuel is injected so best to stop.A lot of people think no problem I will just leave it the fuel will evaporate this is not the case I have had people leave them a week (still flooded).Modern engines are also machined well so the fuel won't go past the piston/piston rings.
As for rectifying the problem there are various ways:
First thing I try is putting the battery on boost so it cranks quick with my foot hard on the throttle pedal,yes it's still injecting fuel but with the throttle pedal down cold air is drawn in and hopefully dries the plugs enough for it to fire.
Second option remove the plugs heat the tips(burn the fuel off)
Option three:yank out the fuel pump fuse and crank over until it ignites/uses the excess fuel in the cylinders.
Option four if it's really really flooded,remove plugs and dry,disable fuel pump,pour a small amount of engine oil into each cylinder,refit plugs and crank,the oil makes a seal around the top of the piston which is good because the excess fuel washes the cylinder bore and reduces compression.You have to be really careful doing this as too much oil poured into the cylinder is bad.Plus using this method causes a lot of smoke from the exhaust when it fires up as it burns off the oil.
Every car is different,most fire up by just planting your foot hard on the throttle,by far the worst vehicle to sort is Mazda Rx8 anything from 20mins-90mins fuel pump fuse out crank,fuse in crank,fuse out and so on.