Doughy or Underdone

Here are some helpful solutions for the common causes:

Underbaked

SOLUTION

Oven thermostats can change over time, requiring adjustments by the baker or calibration by professionals. To assure the correct temperature each time you bake, always use an oven thermometer.
Use a cookie sheet that is 2 to 3 inches smaller than the oven rack. This allows the air to circulate around the sheet, and heats the oven more evenly.
Insulated cookie sheets are two sheets of aluminum with an air pocket sealed between them. Cookies won't get very crisp on insulated cookie sheets and often don't brown well. Try baking cookies longer than called for in your recipe. Realize that most published recipes are not developed using insulated cookie sheets.
Ideally, only bake one cookie sheet at a time, placing it on a rack in the middle of the oven. When baking two sheets of cookies at the same time, rotate the sheets from top to bottom and front to back halfway through the baking time.

Sides prevent the hot air from circulating around the cookies

SOLUTION

Do not use cookie sheets that have "sides." Sides prevent the hot air from circulating around the cookies, and they don't bake uniformly.
Invert pan and use the bottom side for baking your cookies.

When cookies aren't uniform in size, larger cookies will be doughy while smaller cookies may burn. To assure uniformity, use a measuring spoon or small ice cream scoop to transfer the dough from the mixing bowl to the cookie sheet. The recipe will tell you what size spoon or scoop to use