It really depends on what kind of modeling you want to do. Commercial models can be almost any size, fashion and beauty models keep it around 32-36 inches bust, 23-25 waist, and 32-35 hips and must be between 5'8'' and 5'11, runway girls are generally on the thin side and usually 5'10+. Healthy dieting and some moderate exercise will help you get to where you need to be. I walk or run every day, but nothing crazy.