Because of their large size, Newfs are prone to some of the same genetic complaints as other large breed dogs. Hip dysplasia is the big worry, with some Newfs so crippled by the time they're only five or six years old that they can barely walk. Elbow dysplasia is less prevalent but still a concern. Newfs can also suffer from heart problems and cystinuria, both of which are life-threatening. Good breeders will have potential parent dogs screened by a veterinarian so that puppies will be much less likely to suffer any of these complaints. Puppies sold at pet shops do not have parents screened for health issues; do your homework and buy from a good breeder, not a pet shop!
Newfs need to be able to keep cool when it's warm out. Even if it doesn't seem very hot to you, remember that your Newf was bred to stay warm in the bitterest possible conditions. His large size helps retain heat within the body, his fur is double-coated to insulate, his ears lie close to the head to trap warm air, and his limbs are relatively short so that blood circulating to the feet has less time to cool down before returning to the heart. Newfs are therefore prone to heatstroke, which can be fatal. Shaving your dog's fur is not a solution, and in fact can cause other heat-related problems such as sunburn. Instead, keep your Newf inside where it's cool during the summer. He'll be happier inside with you anyway.
Training
Newfs are eager to please and love people, and they love interacting with you. Obedience training can be fun for both of you, and it's very important that your Newf know how to behave. Newfs don't realize how large they are, and they certainly don't realize how scary they look bounding happily up to someone who might not like dogs. They can easily knock a grown man down without meaning to, so train your dog early so you won't get into such a situation.
If you've trained dogs before, keep in mind that a Newf may respond more slowly and take a little longer to learn a skill than you're used to in other breeds. You need a lot of patience, and try to slow yourself down to your dog's speed. He's not being stubborn, he just isn't as quick or agile as some breeds. Most Newfs will work hard just for a hug and some kind words, and maybe a few liver treats. You shouldn't need to resort to harsher methods of training.