Train to muscular fatigue. Many people approach an exercise with a preconceived notion of the exact number of repetitions they will do for each set. (Ten seems to be a popular choice.) These misguided souls are training inefficiently and will never reach their full potential. When performing an exercise, your goal is not a certain number of repetitions. Do not start your set saying, "I'm going to do X number of reps." Depending on the muscle group and your particular athletic objectives, you will probably want to stay within a certain range of repetitions. However, your goal is to fatigue the muscle by performing each exercise (with good form) until you no longer can.
A bodybuilding diet aligns with all the general advice for a healthful diet: A balanced mix of macronutrients and plenty of micronutrients from fruits, vegetables, whole grains, and lean proteins. Even in the bulking phase, the idea is to bulk up by eating more, but sticking with mostly healthy choices. Similarly, in the cutting phase, the goal is to cut out less nutrient-dense foods, not slash calories extremely and give up nutritious foods.