It is important to get your puppy accustomed to getting its nails clipped in order to decrease stress and discomfort in grooming situations. Start slowly and keep the sessions fun by rewarding your puppy for calm behavior.
The quality of an adult dog's nails affects on how often they need to be trimmed. Also the dog's activity level and the surface of where the dog regularly walks on affects the wear of the nails. For example, a city dog walks a lot on a hard surface such as asphalt, which wears a lot more the dogs nails than softer ground in the country side. For maintenance, clip your dog's nails every two weeks, and to shorten the nails, clip them every week.
In every nail there is blood vessels and nerves, which are called the quick. In pigmented nails, the insensitive claw will show as a chalky ring around the quick. In white nails, you can detect the quick as a pink area inside the nail. Clipping the quick may be painful and the nail may start bleeding. If you accidentally cut the quick, don't react scared, but instead keep calm and reward your dog if possible. This gives the dog a positive association to the injury, and your reaction calms the dog down. You can use e.g. corn starch to staunch the bleeding if you make a nail leak.
By trimming your dog's nails consistently, you will reduce discomfort and risk of various injuries. Clipping our dog's nails regularly also helps the quick to stay short.