The first thing you need to do before picking out colors is to decide if you have a Warm, Neutral or Cool skin tone. One way to do this is to take a good look at yourself in a mirror in natural sunlight. Decide if your skin color has more Blue or Yellow to it, or if they are pretty well even.
More Blue = Cool
More Yellow = Warm
Equal = Neutral
Another way to find out what skin tone you have is to compare your skin to the colors Silver and Gold. Generally if your skin looks good with Gold, you have a warm skin tone, Silver means cool, and if it looks good with both, then you have Neutral.
Sometimes it can be hard to tell on yourself, so you may want to ask a friend to help you decide.
Once you have decided your skin tone, it is time to choose a Concealer, Foundation and Powder. Depending on where you buy your cosmetics from, you may have a hard time figuring out which one looks best on your skin tone. Avon products are labeled with a W, C or N to decipher which skin tone they are best for. After this, the best way to choose a Concealer, foundation and powder is to try it out! Generally for concealer, you should pick one that is a shade lighter than your natural skin tone, so that when you use it to cover dark areas and imperfections it will blend and look natural. If you have a lot of red spots (acne, scars, etc.) then you should also look into getting a Green spot neutralizer, you use this under concealer to neutralize the red spot and make it look natural. After you have chosen the right concealer for yourself, you should choose a liquid foundation that matches your skin tone as closely as possible. If you have freckles it is recommended to match the color with your lightest freckles to help even out your skin color. Your powder should match your liquid foundation as closely as possible and be used last out of the 3.
After this you should choose an eye shadow. Again, depending on where you purchase your cosmetics you may have trouble finding shades that look good on you as they aren’t always labeled for skin tones. From my experience I have found that for Cool skin tones, Pinks, Berries and Blue/grays seem to look best, for Warm skin tones Earth tones tend to look best (greens & browns and some reds ESPECIALLY for redheads), and for Neutral Skin tones, I try to combine the 2.
After you have chosen and applied the appropriate eyeshadow, you should apply an eyeliner and Mascara. For people with light colored hair, brown or brown/black is an excellent choice of eyeliner and mascara. For people with Darker hair, Black is best, Although black looks very dramatic on anyone, it is a great choice for evening time.
After eyeliner and mascara it is time to choose and apply a lipstick. Generally you should match your lipstick to your eyeshadow, keep it in the same general color family, so if you are wearing pink eyeshadow, try a similar color lipstick, maybe a shade darker or lighter. Grey eyeshadow looks great with different shades of red lipstick! As a rule of thumb, if your eyeshadow is shimmery, you should avoid shimmery lipsticks, and vice-versa. I recommend to all of my clients to DAB lipstick on, not to swipe it across their lips. By dabbing you have more control over the intensity of the color and you can make a more natural or bold look.
As with everything, this is just a guideline, play around with your makeup, take whatever seems helpful and leave the rest, this is just meant to give some suggestions, the best way to find out what looks best on you, is to try different things out! Good luck!