Coffee cookies are dark in colour, so it is a bit hard to know when these are done. I believe that a change in colour and appearance is the first indication of perfectly baked cookies. If you observe in the image below, you will see the colour of the cookies is dark with a gloss on them, and the shape is perfectly round before baking, whereas the colour changes to a lighter shade with a loss of glossy and its shape changes to a flat after baking. (Image below). So, this is how you can get the first idea of whether cookies are baked or not. The other main indication you can look for in cookies is the firmness of the cookie edges. The cookie edges should not fall inwards when you gently press the sides of the cookie with a spatula or a knife. Rather these should stay firm. But if you find the cookies are easily pushed down, then bake them a few minutes more in the oven.