The Norfolk terrier and its close relative, the Norwich terrier, while tending to be relatively worry free in the health department, are especially prone to dental problems, more specifically, terrier owners and especially Norfolk lovers, are advised to watch out in particular for incorrect bite patterns. Terriers in particular are so inclined to this problem, in fact, that some people even misunderstand severe under bites to be one of the dog's identifying traits (to be fair, this is, sadly, arguably true, given the huge number of terrier house pets whose misinformed owners neglected the problem in the dog's early stages of development). While the severity of the problem with individual dogs is, luckily, rarely debilitating in any way and sometimes fairly inconsequential, any terrier owner or potential terrier owner, especially of the Norfolk persuasion, are advised not to take any chances, because the risk of the problem developing and growing out of hand is very real.
As a preventative measure, it is advised that Norfolk terrier owners take their dog's into the vet for regular dental checkups, especially in the early stages. At least once every few months during the dog's most significant growth period, and certainly more often than that in the event that a problem is detected, or even suspected, by the owner. Regular brushing of the teeth can help as well. It's a common misconception that brushing, in humans and animals alike, is only for the sake of keeping the mouth clean. In fact, the brushing exercises the gums and stimulates blood flow through the mouth, as well as ridding the mouth of bacteria that can get into the blood stream through the lungs, stomach or skin and cause more severe health problems, specifically, viruses that target the heart. Again, this is imperatively true of both humans and animals, so good brushing habits are a must regardless of breed or disposition.
Another measure to prevent the problem of incorrect bite problems the later stages is to feed the dog with dry dog food. The harder consistency of dry dog food provides exercise for the jaw and teeth. This is definitely a must, as teeth are more likely to grow misshapen if they're given nothing to do. Likewise, chew toys are not just for fun, they also keep the jaw from growing complacent. Dogs instinctively chew on bones to keep their teeth in good shape. While an ideal toy is a thick tug of war rope, Norfolk terriers are notoriously headstrong, and their humans are advised to not even bother trying to win the game.
Beyond the above advice, any terrier owner would be advised to associate with other terrier lovers in the area through clubs. The help of a more experienced owner of the same breed is priceless as they can personally show you what to look out for and will notice much more quickly than a first time owner if something is amiss or needs attention.