Just like with being a parent, there is skill involved in being a successful pet owner. There's more to it than just going to the pet shop and getting a puppy or a kitten. You have a responsibility to keep your pet healthy. But how does one do this?
Have your pet spayed or neutered - that is unless you want to use the dog or cat for breeding purposes; take your dog for regular walks, as dogs need exercise just as much as people do; feed your animals at the same time every day and feed them healthy foods, recommended by your vet; make sure there is always fresh water for your animals; take your pet to the vet if it stops eating or loses weight; make sure that your pet gets all the injections and vaccinations it needs; deworm and deflea your pets regularly.
Read more on protecting yourself from these animal diseases.