9. Always use lip liner
The idea behind this rule was to keep your lipstick from bleeding into your foundation. The unfortunate unintended consequence was “coloring book lips”: the look you get when your lipstick wears off and you are left with nothing but a dark outline.
The secret to using lip liner without looking cartoonish is to choose one in the same shade as your lipstick and to apply it all over your lips rather than just outlining them. You can then apply your lipstick over the liner.