I am 13, and wearing a bra size 34c. I really want to have smaller boobs, so I can wear a bikini comfortably, and so I do better in my sports. How can I make them smaller?

You should feel privilidged to have big boobs! :)

To my knowledge, you can't really make them smaller without surgery. Invest in a good sports bra. I've also heard of girls taping them with sports tape, but I wouldn't say I suggest such a thing.

At some point in the future, you may find that breast reduction surgery is necessary for your health. At this point its not. And I doubt is any surgeon would perform the procedure. Its possible your breasts may have stopped growing and your body needs to catch up. A 34C should not be too big for a bikini, shop around for styles that suit you. And yes, go to a good bra shop for proper fitting.

I wouldn't bother! You will grow into them as you get older and grow and fill out.

I hate to be frank, but having big boobs is usually a sign of having more fat on your body. If I were you, I would try working out more and running every day. This should reduce their size. Trust me, you ARE NOT done growing yet. Chances are that your boobs will grow much larger... possibly even a DD. The reason I say this is because the same thing happened to me, and I wish I had done something when I was younger.

The earlier you start, the more likely it is that you will be able to sort of "nip this in the bud."

And if you are worried about bikinis, shop for larges and D- cup sizes. If you are worried about sports bras, try looking at Champion brand for larger cups. Also, you could also try wearing 2 sports bras at once. But as I said, run every day and watch what you eat. DO NOT go on birth control, for this will only make your boobs larger.