First, decide what kind of look you want to create. Do you want to look casual and natural, or sultry and dramatic? Think about where you're sporting your shadow, and what you want it to say about you. Choose light, pretty tones for a picnic in the park, or deeper tones for hitting up the nightlife. Opt for colors that are lighter than your eyes if you want to go natural, or grab some darker shades to get glammed.
Try peach, beige, pink, lavender or lighter browns if you want a fresh, natural look. For a natural look, two shades are all you really need. Ask yourself whether the shades blend in with your skin too much--if so, what's the point of wearing them? You want at least some subtle contrast. On the other hand, there's such a thing as too much contrast. If you have darker skin, don't go overboard with the light colors--stick to sheer ones and use them as a subtle highlight for a medium tone like mahogany. Sweep the lightest shade over the whole lid, extending it slightly above the lid. Then apply the medium tone to your lower lid, as Bobbi Brown et al. say in "Bobbi Brown Living Beauty."
Grab three of your fave complementary colors for dramatic eyes, like a pale green, medium green and deep brown. Apply these shadows the same way. If you have deep brown eyes, this look will really show 'em off. Go with lighter shades of purple combined with deeper tones for a smoky, sultry look, especially if you have olive or brown skin. Pair the shadow with a dark eyeliner. Carefully draw a line that blends right in with your upper lashes, and extend it all the way down your lid to the end of your lashes. Smudge it a little at the crease if you want. Then apply the shadow, following the same method described above. This time, though, you'll finish by dabbing your darkest shade just inside the outside crease of your eye.
Try shimmery metallic colors in medium tones for a subtly intriguing look. Copper, amber, gold and bronze will create beautiful highlights for your peepers, as Rona Berg says in "Fast Beauty." So will shimmery green or light blue. Choose sheer colors so your shadow doesn't have a cakey look.
Trying shadows on your own face is one of the best ways to find out if they really work for you. But getting a pal's opinion is even better. Have an old fashioned makeover party with a bud whose taste you trust, and ask her what she thinks.
If you have a hard time choosing matching shadow colors, don't fret! Many makeup lines do the work for you and combine three shades into one compact.
Play around with different brushes when you are applying your shadow. Different tools work for different looks and a misused brush could be the difference between "streamlined" and "black eye!"