The first step is to sharpen the liner. Do not get too carried away as if you sharpen it too much the end might just fall off and begin degrading too soon. We say might, but we actually mean most likely will. When you are nearing the near optimum level of sharpness, you may want to take slower, shorter turns when it is inside the sharpener. Remember to push it inside the sharpener firmly but not forceful.
The trick to getting a sharp liner is to apply even pressure throughout the stroke. Do not add more pressure or reduce it as this can lead to inconsistencies and leave you with a result that is anything but sharp.
If you are using a blunt liner then you need to be aware of the bleeding effect. This occurs when the liner is held in one area for too long and the substance spreads beyond the desired area and becomes smudged. In order to avoid this use a smooth motion while moving the liner tip across the area and do not, under any circumstances keep the tip in one place for too long.
In case one wishes to draw sharp edges then incorporating a flick at the end of the stroke. Basically line the majority of the lines as you would normally but before you reach the end of the stroke, flick your wrist in an upward motion. This should, with a bit of practice, allow one to draw those sharp edges. Remember to take your time when doing this as it can take some time to practice.
Remember to sharpen the liner using the care tools whenever the tip becomes too blunt. This will maintain the level of sharpness required.