First of all, make sure pets are allowed where you live. Some landlords do not allow pets.
Be responsible! Do your homework and chores without being asked. If you play an instrument, practice it. If you already have pets, even if it's just a fish, take care of it without complaining.
Keep your room clean an organized. This shows that you can be trusted with what you have. Of you are willing to clean your room, you are willing to clean up after your pet.
Research! Find out what the pet of your choice requires. Present a paper of some sort about your pet to your parents to show that you know what they need, and you are willing to care for it.
Be persistent, but not in an annoying way. Don't whine or cry about it. This only tells your parents that you are immature and not ready for a pet. Good luck!!
The creator of this guide has not included tools