When you bring home a new puppy, the dog you already have can feel a little put out. Not only is the new animal encroaching on his territory, she's taking his toys, food and time with his master. You have to show a lot of diplomacy to combat jealousy: Without an equal distribution of resources, your dog can feel threatened by and resentful of his new housemate -- leading to fighting.
Make sure the amount of time you spend with your dog doesn't suffer because of spending with your puppy. Yes, puppies require a lot more time and attention than fully trained dogs. That doesn't mean your dog doesn't need attention. A sudden drop in the amount of time you dedicate to your dog will stress him out. Even when you have the puppy with you, spend time with your first dog, too.
Toys for Everyone
When you have two dogs, you need toys and plenty of them. If your dog and your puppy fight over the toys, take them away and allow them to have toys only at designated times. This helps them learn that toys are earned -- they are a privilege, not an entitlement. When you give them toys, give two to each dog. That way, if your dog steals a toy from your puppy, she'll still have something to play with.
All dogs, young and old, thrive with structured routine. Changing your dog's routine because of the puppy isn't fair to him, and it can seriously stress him out. Do your best to keep things the way they always have been and your dog's jealousy will be minimal. Keep feeding, walking and playing times consistent with your pre-puppy schedule so the puppy won't represent a threat to your dog's way of life.
Giving Alone Time
It's important that your dog and your puppy spend time together and socialize, but you don't want your dog to feel like he isn't special anymore. The dog and the puppy should both get plenty of alone time with you, going on private walks, having separate play dates and enjoying individualized attention. If your dog perceives that his position in your life has been diminished by the puppy, he'll feel threatened and jealous.