Summarize the following:
In order to pinpoint where a bra does or does not fit well, be aware of the various part of a bra.  The cup: The part where your breasts fit into. It’s usually made of stretchy fabric, and can have up to 3 tailored seams. The band: This is the elastic part that goes all the way around your chest. The wings: These are the portions of the band that extend from the end of the cups to the center of the back. The straps: These go over the shoulders and are often adjustable, and sometimes padded. The closure: This is usually a hook and eye set at the center back. However, it can also be in front, or absent. The center gore: This is the part between the cups in the front. If you appear to have 4, you have what is called the “quad boob effect.” This indicates that the cups are too small, and there's not enough room inside. This is especially apparent if you try your shirt on over your bra. If it does, this means that the band is too loose.  Try raising your arms and bending backward a bit to check if this happens. Remember, when you go up a band size, go down a cup size. If it won’t, then the bra doesn't fit.  This could be because the underwire is the wrong shape for your breasts. It could also indicate that the cup size is either too large or too small. You should be able to run your fingers around under the edge of the fabric.  If you can pull it away from your back by more than 1–2 inches (2.5–5.1 cm), it's too loose. If the band digs into your sides to the extent that it causes pain after wearing it, the band is too small. If the band rides up, try loosening the straps. If this doesn’t work, the band is too big. This does not necessarily mean the band is too tight.  Instead, look for bras that have a wider band or a “leotard band” to create a smoother silhouette. Unless the band is causing you pain, don’t go up a band size, otherwise you will not have enough support. This could also indicate that the cup size is too small.  Another solution is to wear a body shaping undergarment. This could mean that the cup size is too big, the style is wrong, or that you have not put the bra on properly.  Try adjusting your breasts to make sure they are centered in the cup. This could also mean that the bra is not right for your breast shape. If your breasts are fuller at the bottom than at the top, you may need a differently shaped bra, such as a “demi cup” or “balcony” style bra. This can cause pain, and other problems.   Straps that dig into your shoulders can cause long term problems, such as headaches, back pain, permanent indentations, and even nerve damage. Try looking for bras with wide, padded straps, especially if you have larger breasts. Shoulder pain could also indicate that the band is too big and not providing enough support. The support should come from the band, not the straps. If you’ve adjusted the straps and they still keep falling, try a different bra.  Petite women and women with sloping shoulders often have this problem. Make sure the straps are set close enough together and are fully adjustable. Underwires that are fitted properly should not cause any pain or discomfort.  If the cup is too small, the underwire may not fit comfortably under your breasts. Also, your individual breasts may not necessarily be the same shape as the manufacturer’s underwires. You may have trouble wearing underwires if you have a higher rib cage. Underwires are not recommended for pregnant women or women undergoing surgery. Some medical conditions may also make it inadvisable to wear underwires. Bras without underwire can be just as supportive, even if you have larger breasts, as long as the fit is correct.

Summary:
Know the parts of a bra. Count your breasts. Check to see that the bra doesn't slide over your breasts. Check that the middle of the bra is lying flat in front. Check that the band doesn't ride up your back or dig into your sides. Note that “back fat,” a common complaint, is normal. Make sure the cups don’t wrinkle or have gaps at the top. Check that the straps do not dig into your shoulders. Check that the straps do not fall off your shoulders. Make sure any underwires are comfortable.