As everyone else is saying, it all really depends on your body type and how much body fat percentage you have. It is important to be eating the right foods up until 48 hours after your workout.
If you have a higher fat percentage, you need to do workouts with higher reps and lower sets in order to tone up and increase your metabolism.
If you have a low fat percentage (your skinny), it is a lot easier to achieve a six pack. Make sure to do workouts that are centered around your core. For example, instead of bench pressing, start with dumb bell presses because it focuses on your core more than if you are bench pressing.
Remember to eat foods that are rich in nutrients such as any type of white meat. Also, peanut butter and cottage cheese are great sources of good protein and good fat.
If you want to start seeing results, make sure you are doing core-based lifting exercises and on the off days you aren't, do ab workouts such as flutter kicks. Flutter kicks work your abs way more than sit-ups and has much less strain on your back.
I recently put up a workout on my website that explains what i do to maintain my abs along with the rest of my body. It's the second post so you might have to scroll down a little. http://www.sixpackshortcutsreviewer.com