How do you train your dog not to attack other dogs?

I set up a play date for my lab puppy and just as the other dog got near her she started to bark viciously and growl. I tried to gain control of her but her nails scratched me up really bad.It is the same with walking her,she is fine walking until another dog passes by she'll get really mean and growl and bark.What do I do?How do you train your dog not to attack other dogs?
Your dog needs to know who is in control. Try getting your puppies' attention by hitting its body, of course not hard but hard enough that your dogs attention is at you. If that doesn't work grab and hold your dog towards the ground. The hold should be firm and place one of your hands on the neck or collar. If your dog tries to move just hold it there longer and repeatly say ';NO';.How do you train your dog not to attack other dogs?
scold it when it starts to attack
Scold her, and try to get her used to other dogs, she might just be afraid. Try dog training classes, there are dogs and they can suggest special training tricks that might help
she's probably just afraid of the other dogs. i would take her to a training class where she can get used to other puppies and you will be in an environment where a trainer can give you suggestions on how to stop her from growling.