The best brands of puppy food should be chosen based on their ingredients, and how they compare to the guidelines set by the Association of American Feed Control Officials (AAFCO) and the National Research Council. In fact, puppy and dog food standards should meet or surpass the minimum guidelines set by these groups.
Many generic brands meet the very minimum of requirements and may lack some of the nutrients your puppy needs, leading to poor growth or even malnutrition. However, that is not to say that the most expensive brand is automatically the best.
Unless your puppy has a health condition that requires a specially formulated food, this is one of the cases where it can be very helpful to talk to someone who has experience with raising (and feeding) dogs -- such as breeders and trainers. Your veterinarian can be helpful as well, but some vets may be biased toward a specific brand that they happen to be carrying at their practice. The same goes for pet supply store employees. They are sales people, and some will push the foods that will bring a higher profit to the store. When choosing a good food for your dog, it can be more helpful to talk to someone who is not beholden to a brand name.
A puppy should be fed three times a day until she reaches about six months old. In many breeds, growth slows down around this age, so unless your veterinarian recommends otherwise, you should reduce her meals to twice a day only -- in the morning and in the evening. Twice-a-day meals will remain the feeding guideline for the life of your dog.
Meals should be given at the same time every day, ideally in an area where she will not be disturbed while eating. When using dry kibble, you might mix it with a little canned or thawed raw meat, plus some warm water to add moisture. You can also alternate the meat with cooked egg or cottage cheese. In addition to the regular food, give your puppy some yogurt a few times a week to improve her digestive health.
If there are times when your puppy does not have an appetite, let her be. It is fine to skip an occasional meal, as long as the puppy is showing a normal energy level and does not skip more than one meal. Place the uneaten food inside the refrigerator (or closed container, if it is dry food) so that it does not spoil and offer it to her again after a few hours have passed.
If your puppy refuses to eat entirely, do not force or coax her into eating by offering meats or foods from your table, or any other type of food that is out of the normal range of dog approved foods. These foods will not provide adequate nutrition, and will only lead your puppy to expect to be given “people foods” from the table. She will never get into the habit of eating the appropriate foods if she knows that you will feed her the “good stuff” as long as she holds out for them. You will need to stand your ground and only offer the types of foods that you will be giving to your puppy/dog over the long term.
It is very rare for a dog to ignore the food that is being offered until it becomes a health issue (e.g., malnutrition, starvation). Once she gets hungry enough, she will eat the food you are placing in front of her. However, you do not want many days to pass before you consult with a veterinarian. If your puppy appears to want to eat but cannot hold the food in her mouth, or only seems to be able to take a few bites from the dish, there may be an underlying condition that needs to be diagnosed. If that is the case, you will need to immediately take her to a veterinarian.