A dog is a lot like a child: they constantly need attention, or they show signs of unhappiness. The success of keeping your dog happy is based on the amount of attention you give him. A lonely dog is a sad dog.
The best way to give your dog attention is to play with him/her. Any kind of toy, either a plush toy with which you can play fetch, or a chew toy with which you can play tug-o-war. Keeping the dog occupied will keep him happy. Giving your dog a chew toy to play with on their own will not stimulate your pet as much as direct contact and attention. In fact, most dogs will play with a chew toy only when they are bored and lonely.
Dogs need to keep active. Take your dog on long walks. Run with your dog. Chase him/her, or have him/her chase you. Keep the dog moving and stimulated. Letting your dog outside into the backyard is not sufficient; they are unlikely to exercise and play on their own. They require your presence, even if it is as simple as sitting in a lawn chair and throwing a ball for your dog to chase.
Nutrition also keeps a dog happy and lively. Although it seems like a good idea financially to buy the cheap dog food, but these brands have less nutritional value. Working out a high nutrition diet is one of the highest paid jobs for vets. With a less nutritional diet, dogs will be lazy and inactive, and since activity is directly linked with happiness, the negative effects can easily be seen. Also, try to serve your dog its food in a hard bowl, such as glass or ceramic. Dogs will not chew on a hard bowl, which will keep dangerous substances, such as plastic or rubber, out of your dog’s stomach.
Keep your dog healthy and active, and you will see a happy pet.