When your puppy arrives home, if he does not eat too well for the first few days, don't panic. Try to avoid tempting him with 'special' food as this could just make him a picky eater. If he continues to be difficult and you have not changed his food for something he is not used to, then the best thing is to put him onto a "starvation diet" this may sound harsh but it always works.
This is how: For his breakfast, give him just a very small amount - about quarter of his normal food sent by the breeder (after all, he is used to it and ate it perfectly well before). Give him nothing more, until his next feed is due. Then give him the same amount again and so on for his normal meals that day. Do NOT give any titbits between meals, but ensure he has plenty of fresh water. The next morning you may give him a tiny bit extra - say a third of his normal amount, and the same for the rest of that day, On the third morning, give him half of his normal rations and so on for the rest of that day. By the fourth day he will be ravenous, so give three-quarters and by the 5th day he should eat his proper amount and will never look back. This method does work, as long as you stick to it. Remember you are being cruel to be kind, it is better for your dog to eat regular nutritious food. If he becomes faddy, he may not reach his true potential, so nip it in the bud at the start.
It is very rare for puppies or adult dogs to starve themselves. If he is the exception and continues to eat poorly then you should seek veterinary advice.
You must ensure that he always has access to fresh clean water at all times.
Most breeders have their tried and tested methods of feeding. If you have bought your puppy from a reputable source, then you should trust the breeder's recommendations. Follow the diet sheet they have supplied, for at least the first few weeks, until your new puppy has settled in. If after that time you wish to change how you feed your puppy, then speak to your breeder for advice. You should make the changeover very gradually, adding a little of the new food at each meal, gradually replacing the old one. After about a week, the changeover will be completed. During this time, you will be able to tell whether the new food agrees with your puppy's digestion. Don't buy large amounts of new food until you are sure.