To get toned overall, you need to build muscle AND have low body fat. It is not enough to just be skinny and have a low body fat percentage.

You need to actually build your MUSCLE so that it shows up. One option for making muscles more obvious is to do very high reps, anywhere from 15 - 20. This will require low weights though.

 Be sure to do some HIIT cardio, to burn any unwanted fat but also maintain your muscle mass. To get a defined six pack, train your ABS with high reps.

Related Questions:

1. What is the best split for muscle gain? Can I gain muscle doing full body splits?
2. Can I do cardio and gain muscle?
3. How should I be training my abs?