First, get start on stage. Perhaps you can get into performing arts in school. From the stage, learn about what is different for the camera. The big thing to remember on camera is do not move around more than is scripted or you will walk out of the camera view. Also, the volume on stage is high for voices and low on cameras because you have mics. On camera ever little twitch or move is caught. So be aware to all the details picked up on camera.