Context: The new year has begun and some people may be looking to 2015 as the year they get a dog. A furry friend will bring a lot of fun and companionship to your family -- especially for urban residents who always feel lonely living in the fast-paced society. But looking after a pet does require some responsibility from the pet owner if you want your new friend to be healthy and happy in your family. The following is a checklist for people who are considering adopting an animal. Where to find a dog There are hundreds of pet shops in Shanghai, big and small, where you can find puppies at a cost ranging from a few hundred to tens of thousands of yuan. The pet shop will tell you some basic facts about dogs of a specific breed. But don't forget to ask about the vaccination status if you are buying a puppy, which needs three injections with an interval of three to four weeks between shots. Another option is to ask your friends if they know anyone with a dog that has recently had puppies. This option is more reliable than buying a puppy from someone you don't know, especially the street peddlers who might carry animals with diseases. Another highly recommended option is to adopt one from an NGO dedicated to providing shelter and protecting stray animals. This is quite practical if you don't care about the dog's breed. Vaccination As a pet owner, there are some things you must do otherwise you may get into big trouble, and one of these is getting your dog vaccinated. Dogs need regular shots to fight against canine parvovirus , rabies and other diseases or viruses. To ensure the vaccines are not substandard, we strongly recommend you get your furry friend a shot from a qualified _ , which may cost a few hundred yuan each year. Another advantage of using the vet as opposed to getting your dog vaccinated yourself, is that the vet will examine its condition to see whether it is suitable to get a shot now and take immediate action if it has an allergic reaction to the vaccine. Because you are advised not to give your animal a bath for one week following its vaccination, you should clean your animal one or two days before the shot if you don't want your dog to get too dirty. Parasite protection As a pet owner, you need to be prepared to get rid of fleas , heartworm , roundworm , intestinal worms and other parasites from your dog. Dogs need regular flea and tick control and parasite protection, even if it does not show symptoms of being affected by the parasite. An adult dog needs to be fed with a tablet every six months to make sure it does not have any parasite. You also need to take measures every three months to help expel fleas and ticks from your animal. You need to learn the signs of a flea bite: they may immediately cause a dog to feel extremely itchy. Within 30 minutes of a bite, they may develop a red bump. Secondary infections caused by scratching are also common. Dog training No dog is born with good manners. Pooping on the carpet, leaping enthusiastically onto guests, pulling so hard that it practically yanks your arm out of the socket when on walks -- that's all perfectly acceptable in the canine world. It's up to you to teach your dog to behave the way humans want it to. Despite the adage(;) about old dogs and new tricks, there are no age limits to teaching dogs. And whether you've got a brand-new puppy or an older dog, the first step is the same: learn how to be a good teacher. Every dog is different and will respond better to a slightly different training style, but these general guidelines apply: stay consistent and patient, and reward your dog for getting it right. 
 Question: According to the article, how many aspects should a pet owner pay attention to?
Output: four