Medium-sized lobsters tails cook in only eight to 12 minutes when immersed in salted, boiling water, according to Better Homes and Gardens. Smaller or larger tails require slightly shorter or longer cooking times. The shells turn bright red when the lobster tails are done.
If the lobster tails are frozen, defrost in the refrigerator for eight to ten hours prior to cooking. When the tails are done, the meat should be fork tender. Drain the lobster tails in a colander to remove excess water before serving. To eat, cut through the shell using kitchen shears to expose the meat, then enjoy with clarified butter.