The things which you should be avoiding the most are a) added sugar (comes in many forms: glucose, fructose, maltose, lactose, corn syrup, cane juice, sucrose and "sugar"). Naturally occurring sugars in foods is fine, but when added, sugar can harm your body, b) Too much sodium (usually added in the form of salt), and c) saturated and trans-fats. Avoiding any significant amount of these will go a long way to ensuring better nutrition. WHOLE foods are always best, since each step in processing will destroy or remove more nutrients. Whole wheat/whole grains, natural fruits, veggies, nuts/seeds, legumes (beans, peas, lentils, peanuts), etc. If you eat mainly whole foods, and a good variety of them, you will get good nutrition!! Almost all diets contain plenty of protein so don't worry too much about that one..... unless you are a "body builder" in bulking-up phase, you don't have to bump up your protein intake in order to build a good amount of muscle.