You start training from the very first day you get your puppy. You train her to follow you off leash in the park, invent some melody to whistle as a recall, eye contact when you call her name, sit, bark for a treat, introduce her to a ball play and tag-of-war without much pulling on her teeth. Introduce her to as many commands as you can - you would polish her performance in the future in many different situations. Average GSD has higher intellectual potential than the majority of breeds and it is normal for GSD to pass Schutzhund obedience at 6 months of age.
Just avoid meeting other dogs for too long and ask people not to touch her - it would teach her bad manners from the start.