Over the past week, I have encountered several clients who said they skipped eyeliner altogether because they "didn't know how to do it." To them I said (1) practice makes perfect. . . you just have to do it, fearlessly, then correct it if it's not right (with Q-tip and eye makeup remover). . . but now I want to follow up with this #2:
Use a soft pencil liner to draw that line on carefully. Then, for extra staying power, go back and trace over your original line with a swipe of liquid liner. Yes, the one with the paint brush. . . the mod-kind a la 1960s. One of my favorite MAC artists referred to this technique as being kind of like coloring. Once you get that initial (pencil) line on, it's easy to follow the line and color in what you have already done.
And speaking of MAC and liquid liner. . . their Super Slick Liquid Eyeliner is my fave (shade "On The Hunt"). Extremely long-wearing, water-resistant, and a beautiful slick/wet finish when it dries ensures your eyes will be poppin'.