Everyone wants a six pack! The problem is true six pack abs are not easy to achieve. You need to be very lean and somewhat muscular at the same time. For most people this is very difficult. I am the kind of guy that gets big, fat and strong, or lean and trim but have never been very lean and muscular at the same time. The key to achieving this mythical state is a great diet, short hard workouts, and the proper exercises to both burn body fat and build muscle. Personally I prefer kettlebells to get lean and maintain muscle because kettlebell training is very metabolically expense and builds muscles at the same time. This also improves the time efficiency of your training session. Instead of "doing the machines" and then hitting the stationary bike for half an hour you can get better benefits than both finished in half an hour with kettlebell training! Is that a deal or what? More calories burned, more muscle built, and all in less time in the privacy of your gym or backyard!
There are literally hundreds of exercises you can do to improve your body composition with a kettlebell or two, but to really work your abs and get that coveted six pack, you need to select the right movements. Below is a great video to show you some effective abdominal movements to really bring out those abs.