You must make sure your brownies are cooked all the way through for starters (check with the old wooden toothpick method and make sure it comes out clean). Most importantly, however,you have to wait for your brownies to cool completely before you cut into them. Brownies may smell delicious right out of the oven, but they will not cut well until the set and cool. If you don’t eat the whole pan in one sitting, make sure to wrap them up and put them in the fridge overnight. They will cut even better once they are cold.