Last time I made a chocolate chip cookies, my cookies became black because I did not know which side of heat to use. Should I heat the oven from the top or the bottom? I thought maybe I needed to heat from the top to help flatten them?
1. Definitely heat from the bottom but bake 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. If the cookies turned black, they simply got overbaked. They will flatten naturally as the dough gets warm in the oven, so no need to worry about that.
2. If perhaps your particular recipe yields slightly "puffier" cookies than you desire, you can try any of these steps:
Add a tablespoon or two of water to the recipe.
Do not omit any sugar from the recipe--the cookies will be puffier with less sugar.
Let the dough become room temperature before baking.
Use the bottom heating element. Direct heat will in effect toast or crisp things in the oven. You don't want to toast a cookie.
My oven when in bake mode doesn't use the top heating element at all, the only way to get the top element to turn on is to switch it to broil.