If you like them gooey, then they need to cook less than if you want them firm. Insert a toothpick in the edge about 1" away from the pan and if it comes out clean, they are done (gooey), if you want them firmer, insert the toothpick in the center and when it comes out clean it is done.
Let it cool in the pan for about 15 minutes, then turn it over to remove it from the pan and finish cooling it on a cooling rack. If you do not have a cooling rack, you can leave it in the pan and set the pan on top of a couple of overturned coffee cups. You want the pan to cool everywhere.
From scratch? I recommend using milk, even if it says use water, it will make the brownies more rich, a little extra chocolate never hurts, make sure you bake in a large pan, at about 400 degrees, and pull them out when a toothpick comes out clean. Make sure that the liquid ingredients, not counting the eggs, are at least room temperature, and maybe even a little warm if possible, blend with an electric mixer, it is far more efficient than a hand and whisk.