Strong Abdominal Muscles
Getting a six pack has always been very difficult for the vast majority of us to achieve. It is problematic because it takes a lot of work to do and requires you to take into account your dietary habits as well.
Firstly you should be aware of your training. You will want to do some traditional crunches of curse but will also benefit from lifting weights that target your whole body and doing some cardio work.
Alongside this training you will want to stop eating any junk food and stick to healthy products that you eat in moderation. This is a great start and there is more on this at truth about abs.