When baking cookies you should bake the cookies on the middle rack.
When baking cookies you should heat from the bottom but bake the cookies on the center rack.
Place a thermometer inside the oven to check that the temperature is accurate--home ovens can be off by 50 degrees or more, making a huge difference for cookies.
350 degrees Fahrenheit is a good temp for chocolate chip cookies for example.
Generally, cookies are baked in a moderate oven — 350 degrees F (175 degrees C) — for 8 to 12 minutes, depending on the size of the cookie.
For chewy cookies, allow them to cool on the baking sheet for 3 to 5 minutes before transferring to a cooling rack.
For more even baking, position oven rack at the center of the oven and bake one sheet of cookies at a time.
If you prefer to bake two sheets, space racks so oven is divided into thirds and switch cookie sheets top to bottom and back to front halfway through baking.
Putting raw dough on cookie sheets still warm from the oven can cause them to begin spreading, leading to burnt edges.
Always allow baking sheets to cool completely before adding more batches.
To expedite cooling, rinse warm—but not hot—sheet under cold tap water.