The giblets consist of the neck, gizzard, heart and liver of the bird as well as the lungs and intestines (though the last two are generally not included in ready-prepared birds). Unless you clean the bird yourself, you will usually find the giblets packed in a plastic bag inside the body cavity. Often, however, they are absent from ready-prepared birds. Occasionally, you can buy them separately from a butcher if you wish to prepare stock.
To make stock for gravy, trim the giblets, discarding the membrane and yellow gall bladder from the liver. Simmer them with a few tablespoonfuls of chopped onion and carrot, a bouquet garni and a few black peppercorns.