Balance is the key to applying makeup to a square face. A square face is one where the width of the face is about the same as its length. Soften the squared-off lines of the jaw and temples by determining where and how to apply the right highlighter and makeup shades.
Determine if your face really is square. Some face shapes closely mimic that of a square, such as diamond and rectangular faces. If you identify the wrong shape, you'll be following the wrong rules. Pull back your hair and trace the outline of your face with lipstick on a mirror. Does the resulting shape look most like a square? If it does, you are indeed the owner of a fabulous square face.
Determine the areas you want to bring out. In this case, it's the center of your face. By focusing on the center, it will draw attention away from a chiseled jaw. Dot and blend highlighter or a lighter shade of foundation on the center of your forehead, your chin and under your eyes.
Minimize strong features with a darker shade. Use a deeper shade of foundation on any sharp lines on the square face, that includes the jaw and near the hairline.
Use a bright (but not clownish) blush on your cheekbones. Smile to create an "apple" on your cheekbones and brush the blush over your cheeks in an upwards motion--applying blush from the outer corner of the eyes to the ear. By brushing upward, you'll elongate the face.
Go light on the eyes. Dark shades cause the eyes to recede. Use a metallic or shimmery pearl or taupe to bring out eyes, and thus draw attention to the center of your face, as opposed to its squared-off sides.
Draw out your eyes with eyeliner. To add length to your eyes (particularly if they are round, which will only accentuate strong features), use a liquid eyeliner and extend the line beyond the outer corner of your top eyelid to create a dramatic cat's eye look. If you're not steady with liquid, try a pencil and you can achieve similar, albeit less messy, results.
Use a light color on the center of your lip. Again, this will pull attention to the center of the mouth as opposed to the sides of the face. Use a lip liner and outline the lips. Fill in the lip with this color, but add a lighter color of lipstick to the center of your mouth. Top the look with gloss, predominantly in the center of the mouth, to further bring attention to this part of our lips.
Pluck your brows so they are rounded. Don't underestimate the power of good, well-groomed brows in a shape that is flattering to your features. A rounded brow would not look good on a round face, so a strong, angular brow won't flatter an angular face. Stick to more rounded brows to provide balance.