How can I get my dog to stop pulling when she is on a leash?

I have a German shepherd that I adopted a couple of years ago. I don’t believe she was ever on a leash prior to me getting her. I have tried everything to make her stop pulling but she doesn’t get it. I have used the prong collar, a regular collar, and even those head collars (she does not tolerate this one very well). I am at a loss about how to train her to be good on a leash. Any advice would be very appreciated.