Liquid eye liner works the best for this trick because it is dark, bold, and precise.
All you need to do is apply a strip of eyeliner on your top lid [from side of eye nearest to nose to side of eye nearest to temple] and keep going until you reach your desired length. As you approach the end, make a small curve upwards to achieve the cat eye look.
I suggest L'Oreal Telescopic Liquid Eye Liner for this trick.
