Spareribs are cut from the belly (side) and have up to 14 ribs per slab (also called a rack). Look for a slab that weighs at least 3 pounds, is well trimmed, and has good layer of lean meat on the ribs, especially on the larger end of the slab. Plan three servings per slab.
Loin back ribs come from the blade and center section of a pig's loin and are also called baby back ribs, because they are smaller than spareribs. Back ribs should be meaty and lean, so look for ribs with at least 1 inch of meat attached to the bone. Each slab usually contains 10 to 13 ribs and weighs 1-1/2 to 2 pounds. Figure about half of a slab per person. These also make great appetizers when cut into individual ribs.
Country-style ribs are the meatiest of the rib varieties and are cut from the sirloin end of the pork loin. They are better for fork-and-knife eating than as finger food and are just as versatile as the other rib cuts. This cut is often used for braising, and it does well in the slow cooker. Country-style ribs are sold in slabs and individual servings.
If desired, cut the ribs into serving-size portions. Using a chef's knife, cut between the rib bones to make two- to three-rib portions.
Before cooking the ribs, you can boost the flavor with a marinade or a dry rub. This step is optional.