If you don't know what eyeliner best suits you here are some facts about different liners to help you decide;)
Pencil liner: this is most popular because its very easy to use, I suggest buying a high end eyeliner in any form because it comes very close to eyes (also with mascara). you need to keep your pencil sharp for an accurate line. You should stretch out your eyelid slightly to make it easy to apply a simple line and wing, the line should be on the lash line for a more defined look.
Liquid Liner: this is usually sold in a pretty bottle with a straight applicator brush for easy an application. Liquid liner is used for a richer colour than a kohl pencil. When it drys on your lashline it doesn't smudge unless its exposed to water but I say that and there are waterproof formulas aswell. Do not stretch your eye when applying liquid liner it will make a wierd line.
Hope this helped:)
Love Jade xx