To achieve legitimate eight pack abs, you'll need two things: extremely low body-fat levels and an impressive degree of abdominal muscle development. Some people are lucky enough to have these qualities naturally or with relatively little effort, but for most of us, it requires a significant measure of effort. In order to progress towards the eight pack of your dreams, you'll have to adhere to a strict regimen of diet, cardiovascular activity and abdominal exercise.
Reduce your caloric intake. Regardless of your exercise regime, you'll never achieve an eight pack if your abdominals are covered with a layer of fat, and the fastest way to lose fat is through diet. Keep a record of the foods and drinks that you consume over a few days, then use the nutritional information available on the packaging to calculate your average daily caloric intake. Reduce this number by approximately 500. Start by eliminating sweets, desserts and soft drinks from your diet. If this doesn't satisfy your caloric deficit, proceed to reduce your mealtime portion sizes as necessary.
Increase your protein intake. While protein is mostly known as a muscle-builder, it also has natural appetite suppressing properties. This means consuming extra protein will make it easier to stick to the parameters of your calorie-reduced diet without cheating. Moreover, protein will contribute to the muscular development of your abdominals over time. As such, aim to consume at least 1g of protein per 2 lbs.of bodyweight daily.
Perform cardiovascular exercise at least three times per week. Contrary to popular belief, it's impossible to "spot-reduce" fat on your abdominals, so your best bet for reducing fat through exercise is cardio. For each session, choose between 20 to 30 minutes of high-intensity activities, such as running, rowing or fast-paced organized sports, and at least 45 minutes of low-intensity activity, such as walking or biking at a relaxed pace. Besides burning fat directly, regular cardio will allow your body to maintain its metabolism in spite of your calorie-reduced diet, accelerating your fat loss.
Perform direct abdominal training at least twice per week. This will develop the abdominal muscles themselves, allowing them to show through your skin and remaining subcutaneous fat in the form of an eight pack. At each session, pick five abdominal exercises and perform each for two sets of maximum repetitions, resting for one to two minutes between sets. For best results, choose from the following exercises, each of which elicits more muscular activity in the abdominals than a standard crunch: bicycle crunch, captain's chair, vertical leg crunch, long arm crunch, reverse crunch and hover.