Concealer is the little white lie of the makeup world -- we all use it on occasion, and no one has to feel guilty about this kind of cover-up. But with all the types of concealer available, women often question how and when to use it.
Concealers come in sticks, pots, cremes, and pencils. Any type will do. It's okay to use your fingertips to apply. Just make sure you dab or pat it on -- never wipe or rub. For the most covert application, use a concealer brush. It helps you to be subtle and precise, especially when you're working on small areas like blemishes (yes, we all get them -- pimples, zits, and the occasional Mount Everest).
Even when you're blemish-free, there are places where concealer works miracles: under the eyes to cover dark circles, on the outer corners of the eyes (where it's often reddish or dark), around the nostrils, and in the dark bluish spots where each eye meets the bridge of the nose (check your face in this place, as most of us get a bit of a dent there). A dot on either side keeps the eyes looking brighter.
Basically, concealer is a slightly heavier version of foundation. If you're using concealer with foundation, go with a color that's one shade lighter than the foundation. These two products work in tandem to bring your face to one tone.
Apply concealer first, to cover dark spots or blemishes, then go over the concealed areas with foundation. If the spots are still dark, you can go back and apply more concealer on top of the foundation. (When I'm working under the eyes, I sometimes add more concealer over the foundation just to make the eyes pop a bit more.)
If you're using just concealer without foundation over it, make sure the concealer matches your skin tone. This can be tricky, since it's offered in far fewer shades than foundation. If the color's too light, you'll actually draw more attention to the problem you're covering. But if you get a great match, you can get by with spot concealer and nothing else on the face -- even with blemishes.
Sometimes foundation alone can take the place of concealer; although it's a lighter formula, you can use it in the same areas and it often does the trick. On the other hand, if you're not wearing foundation, just use concealer.
It's really your choice: foundation alone, concealer alone, or a combination of the two. Another option is tinted moisturizer. If your skin's nearly perfect, it's all you need.