So many people want to achieve this goal, but this task seems very difficult for a lot of people to actually accomplish. Sizing down the midsection needs more than a bunch of crunches to become a reality.
To be able to get those washboard abs that everyone wants you need to lower your level of body fat. Everyone has abs, you just can't see them because of all the fat that is covering them up. No matter how many crunches you do you won't get the results you want by doing exercises alone.
To get the results you want you need to start with nutrition and cardiovascular exercise. Start reducing your calorie intake by 100-150 calories a day until you start to see the results that you require. If you do not see the results you want after a couple of weeks reduce caloric intake by another 100 calories.
When you are happy with the amount of fat reduction, you can add cardio exercise. Try 3-5 days a week for 20 - 25 minutes a session. This should help you to improve your metabolic rate and burn those calories faster. Try to focus on consistency, otherwise you might not stick with the program.
Now that you see the fat coming off you can start with the abdominal exercises. Some effective exercises would be to do weighted leg lifts or holding weight up against your chest while doing crunches. Combining all 3 of these techniques will help create more abdominal muscle and create a much better toned midsection.