When buying a live lobster, people should look at the color of the under body and claws of the lobster and at the size of the antennas, according to Food Republic. On a lobster with a new shell, the claws are clean and a bright-red color. On an old shell, the lobsters have scrapes on the claws and under body from the rocks.
When buying at a grocery store, antenna size is important in live lobsters because they eat each other's antennae. People should buy lobsters with longer antennas because they are new and fresher. If a lobster has a very short antenna, it most likely has been there a long time. A lobster should not smell when it is alive, so smell is not a good factor to consider when buying live lobster.
As soon as a lobster leaves the water, it consumes its own fat and nutrients. Cooking a lobster immediately after it comes out of water is the best way to retain the flavor and protein. There are hard- and soft-shell lobsters. A soft-shell lobster is sweeter, while a hard-shell lobster is tougher. Buying lobster close to the ocean it came from can ensure that it is fresher.