Line both top and bottom lids when you really want the eye to standout, of if the eye is small and needs to be opened up. If you want a more modern look line only one lid, it should be the tip. Get liner as close to the lashes as possible, and don't line the inside rim of your eye. Which eye liner you use is a matter of the look you want and what's easiest for you. Powdery pencil and fat crayon liners are better when you want a softer, smudgier effect.
Creamy ones create a strong line and can also be smudged into a smokier look.
Many women find pencils easier to use than liquid, especially for everyday use when there's no time to fix mistakes. Dark brown is a universal- flatterer. Neutral grays , khaki and browns are also good staples. Black works on all but the fairest complexions, though it's dramatic and intense, and may not be right for everyday wear. This gives you the choice of smudging it into the shadow or leaving it as a clean, distinct line.