In the bakery, the cookies are all lined up in a neat rows, all the same size and round. You can make your cookies look just like those.

There are three things you need to do: make them all the same size, make them round, and bake them the same way every time. 
Here's how to make uniform cookies!
With a scoop, you get the same amount of dough each time so all our cookies will be the same size.
When the temperature is the same, the spread is the same.
With the same surface and the same temperature, your cookies will spread the same each time.