First and foremost, ensure that your dog is sticking to her vaccination schedule. Stick to the schedule recommended by your veterinarian.
Discuss with your vet when and how you should begin socializing your puppy with other dogs. Your puppy will be its most vulnerable between six weeks and six months. This means that you need to use caution when taking your puppy to public places where other young puppies might be around until all vaccinations have been administered.
Even then, no vaccine will protect any dog 100% of the time. Vaccines create antibodies in the animal, but that does not mean that they will not catch the virus later in their life.
If your puppy or dog has caught Parvo and survived, you will be glad to know that the odds of your dog catching Parvo again are incredibly low. It may still be possible, but it is believed that once a dog has caught Parvo, they are then immune from it into the future.