If you're looking to become a principle dancer in general whether NBC, Fox, WB etc, you have to consider the most excellent standards of training available. I was in the acting program at DePaul University but I also had extensive training from Hubbard Street, Miami City Ballet and the Dance Theatre of Harlem in Ballet, Jazz, and Modern. Start with Ballet, the younger the better, for it is the foundation of all contemporary movement. Take Hip-hop or Jazz classes for shows or positions that require a certain style of movement 4 to 8 classes a month for a year. You’re looking to become proficient at picking up the moves fast and with some semblance of timing and grace. You do not need to be the best dancer in the room, rather utility is everything, meaning, are you reliable, do you blend well, are you smiling?