* Don't substitute margarines for butter as many contain more water than oil and may yield undesirable results.
* Be sure your baking powder and baking soda are fresh and active so they can leaven the dough. Most containers are marked with "use by" dates. But to test baking powder, see if it fizzes vigorously when you drop 1/2 teaspoon into a cup of warm water. If it doesn't, toss it. For baking soda, be sure it bubbles and fizzes when a few drops of lemon juice or vinegar are added to a small amount of the soda.
Be aware that baking soda starts acting as soon as it is combined with liquid so if that is the leavening in a recipe, get the item into the oven as fast as possible. Baking powder, on the other hand, must be heated first.
* For best flavor and aroma, use pure vanilla extract, not imitation.
* Use the size eggs specified in a recipe - the wrong size can make a dough too wet or dry and affect the texture of the finished cookie.
* Cool baking sheets thoroughly before adding more cookie dough or you risk affecting the texture of the cookie.
* Shiny, heavy-gauge cookie sheets with low or no sides are recommended. Avoid dark or black cookie sheets as they may cause bottoms to bake faster and overbrown. Insulated cookie sheets tend to yield pale cookies with soft centers - and if you bake cookies on them until brown on the bottom, the rest of the cookie may become too dry.
When other baking pans are used, be sure they are heavy-duty. Cheap pans conduct heat poorly and unevenly and even warp when subjected to high heat.
Cookbook author Lora Brody prefers commercial-weight nonstick aluminum pans made by Chicago Metallic and Kaiser Bakeware. Keep in mind that metal browns more evenly than glass, notes Brody.
* Spring-release ice cream scoops are handy for forming drop cookies quickly and efficiently. They're available in a variety of sizes at kitchenware or restaurant supply stores.
* An easy way to lightly grease a baking sheet is to use the butter wrapper or run the stick of butter over it.
* For easy cleanup and removal of cookies, bake on parchment or foil-lined pans.
* Use your microwave oven for melting butter and chocolate. It's also great for softening cold butter and hard dough.
* Always preheat the oven, which will take 10 to 15 minutes. For best cookie-baking results, be sure the temperature or your oven is accurately calibrated by using a mercury oven thermometer to check it. Many bakers keep a thermometer in their ovens - hanging from the middle oven rack - not on the oven floor - at all times.
* While some experts bake two cookie sheets at a time, turning and rotating them halfway during baking, others prefer to bake a single sheet at a time in the center of the oven. Experiment to find out what works best for you.
* Avoid burning cookies by using a timer - the louder the better.
* Cool cookies completely before storing, and don't mix flavors and kinds in the same container.
* Although most cookies, properly wrapped, can be frozen two to three months, most are best eaten within two weeks from the freezer.
* Generally figure that cookies and bars can be stored at room temperature in a covered container for four to five days (if they last that long) before getting stale.
* If you plan to ship cookies, the two keys to success are to wrap them loosely and individually in plastic wrap and use small containers, advises cookbook author and baking expert Nick Malgieri. "If you want to ship a lot of cookies, get a lot of small containers and nestle them in Styrofoam [or real popcorn] in a large box."