Best Answer: Temperature, time, speed, and additions (sugar, vanilla, etc.), as well as the fat content of the cream. As other have noted, it is really important that the bowl, beaters, and cream be very cold.
The cream should be very cold.
Whipping cream can be taken past the desired point easily so the last bit whip by hand. And better to under whip than over whip.
Beating egg whites requires more in the way of making sure all the utensils are grease free.