The best way to adopt a German shepherd for free is to work with your local animal shelter or breed rescue. Some of these organizations occasionally waive adoption fees.
Even if your local shelters and rescues do not have fee waiver programs, adoption is similar to getting a free dog. Adoption fees are typically fairly small, and they include a lot of care. Dogs from reputable rescues come spayed or neutered, microchipped and vaccinated, and have typically undergone a thorough veterinary exam.
Breed rescues are the easiest way to look for German shepherds, but German shepherds are also available at all-breed shelters. Check in frequently with your local animal shelter, and consider adopting an adult or senior dog. Older dogs are more likely to have discounted or waived adoption fees.
Free German shepherds are also sometimes listed in classified advertisements. However, approach these with caution. Unlike dogs from a rescue, these dogs may have ongoing health issues. They also have not been temperament tested, so you may be taking on a difficult dog with no support. Some classified ads offering free dogs are scams; irresponsible breeders sometimes try to attract attention by advertising a free, then spring a fee on you after you fall in love with a puppy.