From lashline to brow, apply the lightest color.
From your lashline to your crease, put on the next-to-lightest color.
On the outer corner (partially in your crease, partially on your top lashline, in a "vee" shape), you'll apply the darkest shade.
If using two colors, do a wash from lashline to brow, plus a deeper color in the crease.
If need be, you can define the lashline with a well blended wash of liner, so long as you stay far away from liquid and cat eye makeup looks.