Deciphering dog body language is an important part of communicating with your canine. Dogs use posture, facial expressions, and other body language to communicate. Understanding your dog's body language is an important component of responsible ownership.
You should always be aware of your dog's posture because this is one of several ways that dogs communicate how they feel. Once you understand what some in the industry refer to as ETA (Eyes, Tail and Alignment) you can go a long way to making timely assessments not only while walking your dog but with the intentions of other dogs in the surrounding area.

Eyes The longer a dog stares at your dog—close-mouthed and deadpan—the less friendly that dog probably is. Not sure? Imagine another human staring at you the way your dog is being stared at and you'll be on the right track.

Tail The higher the tail, especially the base of the tail (where it meets the dog's body), the more excited the dog is. Don't confuse "excited" with friendly. A friendly tail is wagging big wags and the base of the tail is about even with the dog's spine. A wide, low wag or a happy circular wag are both excellent signs of social intent. A stiff tail held straight up nearly vibrating (short, quick movement) is an excellent sign of scary intent. So is a raised stiff motionless tail. Watch out!

Alignment What is "alignment"? Think straight like an "arrow". The straighter the dog's path of travel toward you is, the stiffer they are, the more arrow-like they appear may signal more risk. A friendly dog is "soft" and wiggles when they wag; a tense dog is not and does not. An arrow-like dog may lie down as you approach. That is not a friendly posture. Think "lion hunting" and you'll be closer to the truth most times.