Directions: If you have nicely defined lips and do not have problems with lipsticks feathering, lipliner is definitely optional. For others, using a lipliner can make a noticeable difference.
Lipliner should ideally be applied before lipstick, to shape the mouth and lay down a "base" for the lipstick to cling to. However, some women find it easier to apply lipliner after lipstick. This can work, but it is not as effective at preventing feathering as applying lipliner first.
Do not attempt to reshape or redraw the mouth with lipliner! As a general rule, those with small lips should stick with lighter, bright colors and those with large, full lips can opt for really any color, but should be cautious with very dark, bold, or bright colors.
Lipstick and/or lipliner almost always cake up if they are applied to the inner corners of the mouth. For the sake of a neat, beautiful application, stop the lipliner just before the mouth's inner corner.
There is no right or wrong pattern to follow when applying lipliner. Whether you start at the lip's bow or on the lower lip line is not important. Precision, staying within the lip line and color-coordinating lipliner with lipstick are what counts.
Your lipliner should not make an obvious line that shows up as a colored border around the lipstick. The goal is to have the lipstick and lipliner meld so you can't see where one starts and the other stops.