You deglaze the pan in order to unlock the color and flavor of the juices that have browned on the bottom as your roast or bird cooked, which you then add to your spectacular sauce or gravy. There are a couple of schools of thought on how you do it. The first step is to remove the excess fat by pouring or spooning it out. Then you have two choices: off the heat, you can pour a boiling stock into the pan and begin to scrape up the deposits. Others would have you put the pan directly over medium-high heat as you add the deglazing liquid, which is wine as often as stock. Putting the pan over the heat may be necessary in any event, as it will help loosen the really stubborn deposits. Once the deposits have been scraped up and dissolved, it is a good idea to pour everything through a strainer to remove any remaining solid particles that might wind up in your sauce.
Madeleine Kamman, the French cooking teacher and author, would have you deglaze a pan only with stock or even salted water, never wine. She says wine must be brought to a boil and simmered slowly by itself to get rid of the harsh taste of the alcohol before adding it to a sauce, or the flavor will suffer. Using wine for deglazing or reducing it with stock will result in disappointment, she says.
And beforehand, while the meat is cooking, you should give some thought to adding small amounts of water to the pan (once the meat has begun to brown and drippings have begun to coagulate) to keep the juices from burning and being lost, at least if you're using a hot oven. You don’t want to have so much water in there that you steam your roast, but enough to save the drippings.