3. Overdoing it. You know how you look at an actress on the red carpet and immediately start arguing with your friends about how old she is, and you end up finding out that she’s, like, 17 or something? It all has to do with the amount of makeup she has on. We all know that you can seriously go wrong with too much contouring, but a lot of women don’t know that overdoing it on black eyeliner or eyeshadow is actually a huge no-no if you want to look your age. Instead, use a gray or brown liner–the muted colors are much softer on the eyes. Or, if you insist on black, keep it to the top eyelid only.