Mastiffs are not an outside dog by choice. Most tend to be homebodies that live for lying around on the couch or a soft mat. They are susceptible to heat stroke and therefore cannot be left outside untended during hot weather. They will bond strongly to family and become depressed when kept away. They are a member of the family and want to be treated as such.
Especially during their growth periods, nutrition is very important to the Mastiff. Overfeeding is as harmful, if not more so, than underfeeding. Mastiffs are genetically programmed to become big and overfeeding them as puppies will not make them any larger as adults, but it can cause growth problems that are potentially crippling. Any reputable breeder who knows the breed can help you determine the correct diet for your puppy. Most quality commercial dog foods that can be found at pet stores are acceptable and watching the condition of your puppy will help you determine the amount of food to give. Puppies should be kept lean enough so that you can see the last two ribs, but not so lean that all the ribs are easily visible. When using a quality dog food it is not necessary to supplement with vitamins and minerals as the dog food is specially balanced for dogs.
Like any other dog, Mastiffs require the usual series of vaccinations as a puppy and yearly boosters. Your local veterinarian can instruct you on what shots are recommended. Other routine health procedures can be determined by your veterinarian.
All Mastiff puppies should be taken to at least puppy obedience classes, not only to learn the basic commands but to also properly socialize the puppy around people and other dogs. Early socialization can help prevent temperament problems later when the Mastiff is older, bigger, and more set in his ways.