The layered tank top look is both a trendy look and a classic staple of female clothing. However, some people have taken that look and destroyed it because they didn't understand the simple rules involved when layering tank tops.
Decide what color, or style, you want to highlight. This will be the top layer. If the tank has a really high neckline this won't work unless it's also really short. You need to pair two tank tops that have different necklines or have different lengths. If they're the same style it won't work because you will only be able to see one top.
Select the top to be highlighted which is the one on top. Find a coordinating undershirt. If your top layer is a solid color without a pattern, design or logo of any sort, you can either choose another solid color or a tank with a pattern to it. If your top layer is a print or pattern you need to select a second top that is solid and is a color that looks good with the pattern on the top layer.
Chose the two tops to be layered and put them on. Look in the mirror. For a perfect layering, the necklines should be separated by at least one inch but preferably two. If the necklines are very similar then the lengths should be at least two and a half inches apart. These lengths provide just the right amount of contrast to achieve the desired look.
Go back to your closet and make another selection if the lengths are unsuitable together.