When your dog is meeting another dog, you should have a firm grasp of their leash or harness. This will help you maintain control of the situation. If your dog has a bad reaction to meeting the other dog, you will be able to pull them away quickly.
Being able to pull away is also important for when the other dog does not know how to greet correctly. You do not want your dog to be in a position where they feel intimidated by the other dog. However, if the dogs start to fight, you should not put your hand by their collar as this will result in a bite. You should try to distract the dogs or get a barrier between them. If this does not work, you and the other owner should pull the dogs away from each other using their back legs.