Get lots of training, lots of practice, years of experience, work hard and be very very lucky.
You can also go onto (www.ballerinagallery.com). It has a list of famous ballerinas and if you click on their names you can see pitcures of them and read a little biography.See how they got started.You also need to work tremendously hard and be able to deal with some pain.You could also visit summer camps over the summer to get a variety of dance training.Auditions for thoes usually start in January and go through March.Look in dance magazines such as Pointe Magazine, Dance Magazine, and Dance Spirit.Thoes magazines have pointers and dance stuff in them.Hope you become a famous dancer.
If you want to be a famous ballerina you definitely have to be dedicated. You have to take a lot of ballet classes in a week, and your toes are going to hurt really bad (pointe shoes kill) You will probably need to go to a few summer dance camps. If you want to become famous, it is good to start out at a ballet company with a lot of other dancers that are really good. Good luck :-)
Well, I would say years of training, dedication, stretching, pilates, and eisteddfods, high marks in exams, and then going through pointe work.......
Anyways.. after a while you can audition for some major ballet company, and hope for the best... then work super dooper hard in classes to get a good role in a ballet!! good luck and happy dancing!!!