There are so many types of cookies out there, and for each cookie there are even more recipes floating around.
But regardless of the type of cookie you are baking, here are some basic tips, starting with the preparations before baking.
1. Use a stainless steel baking sheet. A stainless steel baking sheet or half sheet pan is your best bet when it comes to baking cookies. Some people like the idea of using a nonstick pan, but there are a couple of problems with nonstick. One, it is not truly nonstick. You still have to line the baking sheet to make it easier to remove the cookies. Second, cookies also tend to get darker or burn on the bottom when baked on a nonstick.
2. Use parchment paper or silicone baking mat. Lining your sheet tray with parchment paper makes it easier to remove the cookies. It's cheap and you can find it at any big name grocery store. Silicone mats cost more, but you can reuse them and they last a long time if taken care of. They are also useful for making other sweets such as caramels and candied nuts.
3. Make the cookies even in shape and size. It is important to have your cookies the same size and shape on the sheet tray. If you place the big cookies and the small cookies on the same baking sheet, the small cookies will be well over-baked before the big ones are ready. For scooped cookies, perhaps invest in a cookie scoop. It is a little easier than using a spoon and then sliding the dough out with your fingers. Also, you can get even shapes much easier. If you are making cut-out cookies or slicing cookies from log, try to make the thickness as even as possible.
4. Bake the cookies at room temperature. This will prevent the cookies from being too crispy and hard on the edges and too soft in the center. If you made the cookie dough ahead of time, let the cookie dough sit out for a bit to let them come closer to room temperature. For scooped cookies, flatten them slightly, so that they will spread and bake evenly.