Show your parents that you are ready to shoulder the responsibility. Try with small tasks around the house. Convince your parents that you are a responsible child and will be extremely diligent in taking care of the dog. Try doing chores around the house. Vote for taking out the trash or some such chore. Once your parents are convinced that you are indeed a responsible child, you are well on your way to getting a dog, albeit the road is still long ahead.
A happy parent is a convinced one. In order to convince your parents you must show them that having a dog will not affect your life negatively. One of the main things parents are worried about when getting their child a pet is how it will affect their studies. You have to convince your parents that your grades won’t go down. Once your grades are up and staying there, your parents will be happy and might just reward you with a puppy even without you asking.
Do the research. It is essential that you know everything when it comes to dog. From the address of the local shelter to the nearest vet. You should research the cost of the dog itself, how much will it cost to feed it, give it shots etc. Armed with this knowledge not only will you be able to present a better case to your parents but you will also be able to show them that you ARE indeed responsible enough to take care of a puppy.
Prepare a list of the advantages of getting a dog. The best way to convince a parent of anything is to tell them the positives of it. Think about the advantages of getting a dog and communicate them to your parent. Tell them that walking the dog will give you exercise as well. The dog can also be a guard dog to warn against intruders. Once you list all the positive aspects of getting a dog, you might just convince them to get you one.