Despite its name, a boiled egg shouldn't be boiled (which will yield rubbery results) but rather immediately removed from the heat once the cooking water comes to a boil. Place eggs in a saucepan large enough to accommodate them in a single layer. Fill pan with cold water, covering eggs by 1 inch. Bring water to a boil over medium-high heat. Turn off heat, cover, and let stand 90 seconds to 2 minutes for soft-boiled eggs, 1 minute 45 seconds to 2 minutes 15 seconds for medium-boiled, and 11 to 12 minutes for hard-boiled. Once the hard-boiled egg is cooked, transfer it to a bowl of ice water (this will prevent discoloration and facilitate peeling); let stand 2 minutes, then crack by gently pressing egg against a hard surface. Peel under cold, running water.
Boiled Egg 101
Martha Stewart Living, May 2006