A marinade will keep a roast moist and will infuse it with extra flavor and tenderness. Most marinades include cooking oil, an acid like vinegar or citrus juice, and spices and flavorings. Marinade recipes are as numerous as personal tastes, calling for such ingredients as pomegranate, pineapple, molasses, ginger, bourbon or coffee liqueur. Use 1/2 cup of marinade per 1 pound of meat and marinate, covered, for up to 24 hours in the refrigerator. Don't marinate in metal containers, which react with acids. If you're running short on time, use an injector needle and inject the marinade directly into the meat.

Brining is a technique many professional chefs use. The process is similar to marinating, in that the roast is submerged in a solution for several hours to add moisture to the meat. Recipes typically call for equal parts salt and sugar, with seasonings and a little oil. The salt can be kosher salt, table salt or sea salt, depending on your tastes and budget. Because the meat will be saltier using this method, go light on any additional salt or blended seasonings containing salt.

Although cooking times vary according to the size of the roast, cooking a roast slowly is the key to keeping it from becoming dry. Boneless center cut roasts will need a slightly higher oven and internal temperature than loin roasts, but in general, the internal temperature of the roast should range from 150 to 160 degrees Fahrenheit. After removing the pork roast from the oven, let the roast rest for 15 minutes to allow meat fibers to reabsorb the hot juices from the meat. This is another key to keeping the meat juicy.

Slow cookers are a way to cook a tender pork roast without marinades or brining. Some recipes call for the roast to be lightly browned in a skillet on all sides before placing in the slow cooker, but it's not necessary to make the meat juicier. Cook on low for seven to 10 hours, avoiding the temptation to remove the lid often to take a peek. Opening the lid contributes to making the roast dry and lets the heat out. Adding vegetables, onion soup mix and a little Worcestershire sauce can also add flavor and moisture.

Even an already moist pork roast can benefit from a rich gravy. The traditional style calls for pan drippings left over from cooking the roast combined with melted butter and flour or cornstarch. For a different taste, add spaghetti sauce, dry red or white wine or other favorite alcohol, and experiment with seasonings like thyme or rosemary or even dry salad dressing. To avoid lumpy gravy, gradually whisk flour into the butter and then slowly add the liquids.