I must set everyone straight on this. It is probably the most common exercise myths I hear.
"Doing crunches will get you a six pack"
Whilst in the gym I spotted a girl I knew. She had been doing crunches for about half an hour (with short breaks) I went and sat next to her and asked what she was doing,
"Oh I really want a 4 or a six pack for my holiday next week"
She is not the slimmest of people I know and does have a fair amount of excess body fat around her middle
So i began to explain... If you have a layer of fat over your abdominal muscles then you will not be able to see your muscles and therefore will not be able to see any six pack. You need to reduce your body fat in order to achieve your six pack.
If you want one, see previous post on goal setting, as getting a six pack for next week with out surgery is impossible!
She accepted this and decided on going for a run the following morning. This delighted me, the only thing that delighted me more was that before she left I went to the bar to get a drink and she was buying a chocolate muffin :)...we will tackle that one next time!