Summarize:

It's no myth that certain exercises can make your breasts look perkier--and therefore, bigger. Hit the gym and do some moves that target your problem area. For example, you can do multiple exercises with a light set of weights. Try weighted cross-punches and chest presses.  If you are having trouble, don't be afraid to ask the staff at your gym for advice--that's what they're there for. To make this more enjoyable, grab a friend and do your work-outs together. Hormone therapy is not for everyone, but it can be really helpful for those who have (or are recovering from) a medical condition. Breast tissue is very sensitive and can be very responsive to changes in your hormone levels. Often, these changes result in growth.  Ask your doctor if a medication that adjusts your hormone levels is right for you. One of the most common pills is the prescription birth control pill, which has a common side effect of breast growth. For many women, having larger breasts goes hand in hand with growing older. Some women develop more slowly or at a later rate than others. Your age can play a large role in the size of your breasts. Breasts develop during puberty and again during a woman's childbearing years. To have larger breasts, sometimes the best course is just to be patient and let nature take its course. In addition to being composed of breast tissue, breasts are also made up of fat tissue. Therefore, when you gain weight, you typically gain it in your breasts. If you are unhappy with your chest size, ask yourself how you feel about the rest of your shape. Is it possible that you are too thin? A healthy diet and exercise regimen can help you achieve the body shape that you want.
Exercise. Take hormones. Grow up. Gain weight.