You can't because God gave you that body you have. Every person has a unique custom body and we should appreciate the one we have.
My Answer-
I know that some people hate their nipples, mostly me, so I found a solution. I know you should love who you are, but this sometimes causes pain for people. Studies show that an overcollection of protein (from what you eat) in the body will cause hormones and growth cells to make nipples grow. You can stop this by only eating your daily amount of protein needed. Also, at a young age if young girls (boys?) want their nipples to not grow very big, they can drink more sugary drinks. I'm not saying at an unhealthy and gaining weight rate, but just more. The sugar going down your digestive system will spike up your growth cells and make a plinstphere called mettisohgin that will disrrupt the growing of your nipples. If this is ongoing, you'll grow up flat nippled. If you already are an adult, there's not much more I can say than eat less protein or just get surgery. (The surgery is less expensive if you tell your surgeon about this Wiki Answer, a nurse typed this up for a program)
My Answer, by Nurse Hillary VonMiccay
The same way you make a guy's nipples hard.
Nipples will darken during pregnancy.
you need to suck them
you make them bigger\
surgery
so you can watch them make out
Impossible
Ice them
Yes
Sharper!
Not possible... do crunches the entire hour?
You can make a girl orgasm but having intercourse faster or rubbing her clit whilst having sex or sucking her nipples/ rubbing her nipples