You should be doing Breast Self-Exams (BSEs) once a month for any changes. It's hard to remember, certainly, but make a habit of doing it on the same day of each month and it will get easier. If you think it will motivate you, try making it a fun thing-- buy special lotion just for self-exams, have a BSE theme song, light some pink candles, make some gynocentric treats, whatever will help you remember.
Breast tissue is naturally lumpy and bumpy, so it's best to get really well acquainted with yours so that any changes will stand out. Keep in mind that your breast tissue will change throughout puberty, and they might feel a little different while you're on your period. Your breast tissue reaches pretty far-- up into your underarms and right beneath your collarbone. It might be easier if your breasts are slippery, so you could try doing this in the shower while you're soapy or when you're putting on lotion. Start by putting your left hand on the back of your head, and checking your left breast with your right hand. Use the pads of your three middle fingers and move in small circles over the entire area of your breast. There are a few different recommended patterns-- you can start on the outside and feel your way to the nipple using progressively smaller circles, or try starting on one side and feeling in an up-and-down pattern. Whatever you choose, use the same method consistently. Do this for each breast standing up, lying on your back, and lying on your side. Next, do a visual check-- stand in front of a mirror and put your hands above your head, then examine your breasts from all angles, checking for lumps, puckering, discoloration, or any other suspicious changes. Put your hands on your hips and do the same, then lean over and check them from that angle.
And, you're done! Before you get dressed again, take a moment to remind yourself that you have the rack on an angel. (Does anybody remember that Simpsons episode?)
Testicular cancer is the most common cancer among young men. This self examination is a little bit harder for me to explain because, despite many suggestions from various well wishers, I have yet to (literally) grow a pair. You dudes should also feel free to try to make it a fun thing, maybe by getting a special, um, self exam... chain saw? Truck?
Ha. Just kidding! You're allowed to like candles as well, obv. Theme songs too.
So, to check your testicles, I'd suggest getting in the bath or shower first. Roll each of your testicles between your thumb and fingers individually, looking out for lumps (which can be as small as a grain of rice), swelling, discoloration, and general achiness.
There are a few things that you'll notice that are completely normal: once testicle might be a tiny bit bigger than the other, and you'll feel your epididymis, at the top back part of your testicle-- it's soft, rope-like, and tender.
And you're done!
Good work, folks! Give yourselves a high-five.