How to get bigger breasts or how to increase my breast size?

It is understandable that women and especially teenagers in the USA (and elsewhere in similarly affected cultures) are very self-conscious about their breasts and many worry about their breast size. But the fact is, there is not much you can do to change your breast size - for smaller or bigger. Consider the following things that will NOT make your breasts bigger:

• There is NO food that will make your breasts bigger.
• Exercising in general will not help much. Breasts do not have muscles. If you tone your chest muscles that are underneath the breasts, the effect will be slight (see below for more).
• Sleeping position has no effect on breast size.
• Nor will wearing bras or not wearing bras.
• Rubbing or squeezing won't affect breast size.
• Nor do they get bigger when a woman starts having sex.

So what will affect breast size?

• Mainly your genes. Look to your mom, sisters, aunts - their breast size will usually give you an indication of your final breasts size.
• Breast growth during puberty is driven by two hormones, estrogen and progesterone. Hormonal imbalances could therefore affect breast growth.
• Breasts contain fat, so slim and thin people often (not always) have smaller breasts than overweight/obese people.
• If you gain weight overall, some of that fat goes to your breasts. Exception: it is possible in certain situations to only gain fat in your waist area or abdomen (pot belly). But if you're overweight in general, with fat all over, then losing weight WILL cause your breasts to be somewhat smaller since you will lose fat from all over your body. Anorexic girls typically have very very small breasts.
• An actual injury (like cutting) to the breast bud may prevent the breast from developing right.
• Breasts WILL grow during pregnancy and stay bigger during breastfeeding. Once you start the wean, even partially, breasts will diminish in size because there is less demand for milk. After total weaning, breasts will usually go back to pre-pregnancy size (though sometimes they end up smaller than pre-pregnancy).
• Breast augmentation surgery is the only sure way, but undermines your ability to FULLY breastfeed, and can often have SERIOUS health effects.
• Birth control pills containing estrogen sometimes make one's breasts larger as a side effect. This does not happen to everyone taking the pill though.
• The various herbal pills for breast enhancement, it's hard to say... They seem to be effective for some women, and often not. 
• What about taking extra estrogen? Theoretially this might work. BUT if you are a woman, taking extra estrogen on top of what your own body already produces will definitely increase your breast cancer risk, may cause nasty PMS, and other unwanted side-effects as well.
• Toning/exercising the pectoral muscles: If you really get the muscle under the breast to grow bigger, that DOES have a slight effect on the overall appearance of your chest, and can make the breast appear a tiny bit bigger. Read the words of one female softball pitcher:
  "I have been a serious softball pitcher for the past 10 years of my life and for this reason my right breast is much harder and feels more muscular than my left and is also more perky (I pitch with my right arm in a windmill motion). The difference is not incredible, but it is certainly noticeable. Also, a lot of my friends are softball players and other pitchers have the same issue."
  How much exercise is needed for this is an open question. So it is possible to "push" your breasts out a little by building up your pectoral muscles (inclined/declined/flat pushups). Technicallly it is an illusion since the breasts don't get any bigger.
• The bra industry has created numerous breast enhancer things such as silicone enhancers, gel-filled bras, padded bras etc. to create the illusion of larger bust.
• BRAVA - a vacuum bra system that is supposed to induce breast tissue growth by applying a steady vacuum pressure, but apparently does very little. The website BRAV-ARGH! (now defunct) had many failure stories by women who tried it.