Start your makeup with foundation. This is the base which determines the final effect.

Artificial suntan
Apply a couple dots of color on areas of your jawline or near your nose (the inner wrist or hand aren’t the best spots, contrary to popular belief – skin on your hand has a slightly different colour than on your face).Take a good, long look – near a window. Ask to borrow a hand mirror and stand near a doorway, or step outside, to see which foundation looks best in the natural light. The right shade is one that you can’t see because it blends in so well. Do not believe the shop assistant convincing you to buy darker colour so that your skin will look suntanned. Foundation must be invisible!
Too oily, too dry
Pick the right formula. If you’re oily, look for words like “oil-free” or “oil-control” on the bottle. Got dry skin? Go for moisturizing foundations with “hydrating” or “moisture-rich” wording on the bottle. For combo skin, determine if you’re more oily or dry and go from there. Cream-to-powder bases work great for combo skin.
Without warm-up
Do not apply foundation on your face straight from the tube. Do you remember your grandmother saying that all cake ingredients should have the same temperature in order to mix well? That rule is also true for foundations. If you want it to go well with your skin, it must reach body temperature. It will be enough keep a dash on the outer part of your hand to warm it up. Then, apply foundation with the tips of your fingers or a sponge. If foundation has got right temperature it won’t divide into layers under the influence of fatty acid of epidermis. It will last longer and be less visible.
Surprise cocktail
You shouldn’t mix cosmetics of different brands since they contain different chemical ingredients. They have different properties – matting, moisturizing, radiating. Mixing different foundations (e.g. in order to get the right colour) or combining them with cream (to make lighter) may bring surprising results. The least harmful will be when your foundation will go off. But such experiments may even irritate skin or cause allergy.
Straight onto skin
Foundation should be applied on protective-moisturizing cream. You tend to apply it straight onto skin as you  believe it lasts longer then. It’s true that excess of moisturizing cream may cause that your foundation will disappear more quickly, but you can fight with that. After having applied cream, wait a moment for it to absorb. Get rid of excess using a tissue. Without a good moisturizer your skin will be dry and pinched, and foundation will gather in creases and wrinkles.
Masked
Nothing looks worse than a mask on your face – when you can see the border between foundation and skin colour (at the jaw line). How to avoid it? Try to apply foundation in the natural light as artificial light make you focus mainly on face so it’s easy to forget about applying foundation on neck and cleavage and smudging it near ears and temples. The border between foundation and skin must be invisible – cover it precisely with the tips of your fingers or a sponge.
Excess of foundation
If you think your skin is ugly, do not hide it under a thick layer of foundation, but make an appointment with a  dermatologist. Foundation’s aim is to hide the skin defects by balancing skin natural colour. In accordance with new trends in makeup, foundation doesn’t have to be applied on the whole face, but only in those parts that need correction.


source: http://www.beauty-tips.net/makeuptips/general/art-of-camouflage.htm