Answer:
This is a question I have to answer alot, and a good one too. All you have to do is put your middle finger of the hand the same side of your eye (if you were lining your left eye, you'd use the middle of your left hand, and vice versa), and gently pull, so the eye is closed, but you can just see a little. There are many different methods for different types of liner, but here are my personal heroes:
LIQUID EYELINER: Whilst your eye is in the position described above, paint a line as if you are painting the base of the eyelash, and it should come out in a thin line on the lashline of your eyelid.
PENCIL EYELINER: It is harder to get a thin line with penils, no matter how sharp they are, but it is possible with this method: Colour half of your eyelid, witih the eyeliner, and use a folded up make-up wipe(baby wipes are just as good) to perfect the line by wiping away unwated liner, so you are left with a thin line.
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