There some ruels for this case:
1) DO NOT RUN.
2) You must stand and do not move.
3)Do not look in to dog's eyes. They can understand this sign as an "attack invitation".
4) Do not laugh. This mean that you want him to see your teeth. And dog can understand it as if you wanted to seem more strongly than it.
5) Try to use some training commands, this can mess the dog.
6)Your voice must be calm and not loud.
7) If the dog attacking you, try to protect your neck.