Fitness: When you want to get fit you should include the 3 pillars of exercise. Resistance work or weight lifting, stretching exercises and cardiovascular exercise. Without all of these basic parts of fitness in your workout program, you will eventually run into problems in flexibility, strength or heart health. Fitness is about doing all of the above, not just parts.
Nutrition: Small frequent feedings of natural and unprocessed foods will beat any "special" fad diet for improving fitness and losing weight. Your body is made of what you eat so you must make sure that you are only putting quality foods into your body. A well balanced diet of nutritious carbohydrates, fats and proteins from natural sources will keep your body fueled with nutrients.
Exercise: About 60 minutes a day of moderate physical activity is needed to prevent weight gain. For those who have lost weight, at least 60 to 90 minutes a day is needed to maintain the weight loss.