According to Serious Eats, eggs should be placed in water that already has boiled and left to simmer for 11 minutes to hard boil or six minutes to soft boil. They are then ready to eat hot or serve cold after chilling in an ice bath for about 15 minutes.
Serious Eats recommends several tips that improve boiled eggs. A very fresh egg tends to stick to its shell. If eggs are a few weeks old, they easily slip out of their shells. The starting temperature of eggs doesn't affect the cooking process. Room temperature and cold eggs work equally well. However, once the eggs are cooked, it is easier to shell cold eggs.