Sometimes it's hard to know what your dog wants and needs. The best way to figure out what you puppy wants is to try and read its body language. The best way to do this is to simply observe. Watch you dog as he plays and how he interacts with other dogs. Watch different parts of his body and notice what he does.
What the tail tells?
The tail is often the best indication and the easiest way to recognize the mood of your puppy. Rapid and loose tail wagging usually means excitement. When a puppy wags his tail slowly and stiffly, in line with the back, he is expressing anger.
When his tail is clamped down low and tucked between his legs is a sign of fear, while a nervous dog will wag his lowered tail stiffly. Of course some dogs carry their tails clamped down naturally, but more often than not the tail is a good way to judge a dog’s disposition.
Facial expressions and ears are also a good way to sense your puppy’s mood. When they are perked up and alert it means he is interested and curious about what is going on. They will be flattened when he is afraid, submissive, or expressing pleasure. If his eyes are wide open he may be playful or aggressive.
All in all, the best way to read your dog's body language is to just observe how he acts. Notice when he is being aggressive or playful and notice his tail, eyes, and ears. These are the most common and easiest ways to tell how your puppy is feeling.