Turkey basters fall into three categories: fats, glazes and stocks. Pan juices, the term for the collective gelatin, fat and moisture rendered from the turkey during cooking, fulfill the main purpose of basting -- to moisten -- but aren't always ideal. A combination of fat-, glaze- and stock-based liquids, on the other hand, produces different results, such as browning and aromatizing, to your specifications.
Water-Based
You should use water-based basting liquids, such as stock and broth, throughout roasting. Homemade stock or broth is ideal: Simmer the carcass of a roasted chicken in about 8 cups of water until it reduces by half its volume. Then add a diced onion, a diced carrot, a bay leaf and a few black peppercorns and cook over low heat for an hour. Ladle or spoon the stock over the turkey every 30 minutes during cooking. If you must use canned broth, make sure it's low-sodium or sodium-free.
Fats and Sugars
Apply oil before you slide the turkey in the oven and, if you use butter, at the end of cooking to take advantage of its browning effect. Start basting glazes over the turkey when it reaches an internal temperature of 155 degrees Fahrenheit and every 15 minutes thereafter. Make a basic glaze by combining 1 part sugar and 1 part acid plus flavorings to taste. For example, heat 1/2 cup brown sugar or honey with 1/2 cup cider vinegar in a saucepan over low heat until syrupy; add Dijon mustard and fresh herbs to taste. Warm the glaze before you baste.