Learn your five basic tastes, most people don't get balance right, they can balance sweet and salty but they don't know how to balance sweet with sour and bitter with savory. Once you learn how to balance you can turn any dish into a flavorful dish. Learn your savory ingredients such as Soy Sauce, Truffles, Mushrooms, MSG, etc. Then learn your bitters, they are the hardest. If you make something too sweet balance it with lemon juice or vinegar. Too sour brown sugar, molasses. Too bitter use soy sauce.

As for overcook / undercook as other have suggested, get a good stick thermometer and use it religiously. I have cooked since I was 8 years old in a family of excellent cooks and went to culinary school and to this day I still use a thermometer.