Having six pack abs is a mark of extreme fitness and dedication to staying fit and healthy.
Not only do you need to be in great shape muscularly, but also you need to have low body fat.
You can be in great aerobic shape, but without muscles, you won't have six pack abs - they are muscles after all.
 And you can be extremely muscular, but unless you have low body fat, your abs will simply not be visible.
I like to break my abs exercises into three categories.
1) First there are exercises that work the abs directly.
To build muscles you need to exercise them.
There are plenty of choices, but for me simple crunches work best, although the best exercise for you may vary.
I do 3 sets of 30 repetitions two to three times weekly.
I like crunches because not only are they effective but you can them anywhere, not only in the gym.
For example I can easily do them in hotels rooms while traveling, in my office, or at home late at night or early in the morning as is convenient.
2) Whole body exercises are also great.
For example my abs get an enormous workout when I'm working out in the gym doing exercises like squats and deadlifts.
Yes, these whole body powerlifter type exercises really do work the abs big time, but if they're not for you, there are plenty of other options.
Ever play basketball or soccer when you haven't for a while and find your midsection sore? Yup, sports like these are also great.
3) Aerobic exercise like running, biking, and swimming burn off fat.
 As mentioned above, you need to burn off fat, and if you don't get regular exercise at work or perhaps playing sports, adding aerobics can help burn that body fat to make your abs visible.
Even just walking a few times a week during lunch is infinitely better than going to a Chinese buffet or deli! There you have it, the three types of exercises to help you get six pack abs.
It requires some dedication and commitment to being healthy and in shape, but you'll look and feel great.