Before you make up your next face, there are 10 crucial no-nos we'd like you to know so you don't end up on this list. To ensure your efforts aren't wasted, we asked celebrity makeup artist Fiona Stiles to share her expert beauty tips on nipping these common mistakes in the bud.

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Problem: Too thin, unflattering brows. "When you get a clear look at yourself or have been reprimanded by a friend or professional that your brows are too thin, step away from the mirror, put down the tweezers and start from scratch," says Stiles.

Solution: You need to let your eyebrows grow back in -- all of them. "This is one of the most difficult beauty dilemmas to address because it is so tempting to clean up all of the new hairs growing in," says Stiles. "But you have to let them all grow in to really see which brow shape will best compliment your face."

To quell the urge to pluck, try masking new growth by filling brows in with cake or liquid eyeliner (try Laura Mercier Eye Liner, $20), which allows you to control the density of pigment and even paint on faux hairs if you need to. "For best results, use a very fine, thin, long brush (like Shu Uemura Natural Brush 2R, $14)," says Stiles.

If you are blonde or brunette, use a light/dark brown color. If you have dark brown or black hair, use a black cake liner, keeping it very diluted and building as you go. Also, if you can't afford to see a brow professional regularly, just go a few times until you learn the best shape for your face and have mistakes corrected so you can better maintain them yourself.

Problem: Dark lip shades (such as colors in brown, black, purple or maroon -- think goth) can look aging.

Solution: Avoid lining lips with dark lip liner at all costs, especially if you're not planning to fill them in. If dark lips are a look you're deeply attached to, try a different version of it. Shift to a dark lip gloss if you must, or a sheer version of what you're used to. Try Clinique Almost Lipstick in Black Honey, $14,which is a sheer but deep berry color. Another option is to try a sheer lip pencil if you want your look to last, since glosses and sheer lipsticks tend to wear off more quickly. Reapplying more often is a minimal trade-off for a more youthful and modern look.

Problem: You may not be able to see that your foundation ends in a line at your jaw, but everyone else can. Blending is the key to a flawless face. If your blush sits unblended on your cheeks or the little eye shadow you do wear is just plopped on your lid, it's going to look like you're wearing more makeup than you really are.

Solution: Only wear foundation where you need it and only blend past your jawline if your face doesn't match your neck. Other than that, the key is to get the right tools. "A few good brushes will make the difference between makeup and blended makeup," says Stiles. (Try the MAC 190 Foundation Brush, $32, and Sonia Kashuk Tools Powder Brush, $19.99 at Target.) Latex wedges (like the beautyblender, $19.95) are also good for blending foundations and blushes as you can easily dilute color with a few swipes if you've applied too much.

Problem: This happens to every woman. Even if you've found the perfect color for your skin, the foundation you buy in August will not work for you in February. Also, watch out for foundation that oxidizes throughout the day and changes color.

Solution: Every woman should have at least two different colors of foundation, but three is better. That way you always have colors to mix to get the right color for your skin year-round. Focus on finding a good formula that works with your skin tone and doesn't turn orange (from oxidation) as it interacts with the oils in your skin. (Keep in mind that your face should look like it matches your body. Sheer formulas are better if your face is paler than your chest. Tinted moisturizers are terrific if you don't need much coverage.) The same holds true for concealers. (Tip: Use under-eye concealers that have a subtle light reflective quality and use matte concealers to hide spots.) Also, using a truly translucent powder (like Physicians Formula Organic Wear 100% Natural Origin Loose Powder, $13.95) when you set your foundation (and for touch-ups during the day) will help combat a shift in color.