Dogs are experts at reading our body language because they are pros at using their OWN bodies as a way of communicating with us. When you think about it, its really the only way (besides barking) that they do "talk" to us, and to other dogs, too.
Does your dog nudge your hand sometimes? Its a pretty good guess that he is asking you to pet him. When he drops a ball next to you and then looks from the ball to you, you probably figure that he wants to play. These are just two examples of how dogs communicate with their bodies.
Your dog watches you all the time. Does he get excited when you put on an old
pair of running shoes? He's watched you put them on before taking him for a walk many times, so he knows what happens next. He probably gets excited and wags his tail. Now YOU know what he is saying "Let's Go!"
You can learn your own dog's language by watching him. After awhile, you'll start to know what he is thinking, and what he will most likely do next. So next time when he looks at your sofa, then walks over to the sofa, then sniffs the sofa, you might guess (correctly) that he is about to jump up on it. If you don't want him on the sofa, you can stop him BEFORE he gets on it.
After awhile, you'll be (almost) as good at reading your dog's body language as he is at reading yours!
For fun, try taking a dog body language quiz by clicking HERE.