No matter how much faith you have in your fish seller, refuse outright a lobster that has already been cooked, and look instead for the most active specimen on the stall. The lobster should struggle vigorously when it's picked up to be weighed and should keep its wide caudal fin folded under its body.

Jonathan Cartwright, The White Barn Inn, USA
Usually you can buy shedders (soft shell lobsters) for less money than hard shells but the yield from these lobsters is only half what you get from a hard shell. What's more, the flesh is softer and mushier since the lobster is using its own muscle mass to produce a new shell that will gradually harden over a month or two.

We use hard shell lobsters weighing between 1 and 2 pounds, which are approximately 7 to 10 years of age. A lobster will shed its shell a couple of times a year until it reaches the age of 7 years, each time increasing its body mass and growing a new shell. Lobsters consume their old shed shells. After 7 years the process is reduced to once a year and then at 8 and 9 years it slows to once every two years, while the rate at which the lobster's mass increases slows down as well. A lobster can live as long as one hundred years.

The animal's abdomen and tail contain the meat. The coral is found near the head. Consider saving the shell for making sauces or bisque.