It's important to understand what dogs are saying with their bodies, not only to know your own dog but to better predict what other dogs are doing.
To really read dog body language takes experience. I encourage you to watch your own dog(s) and others. Go to the dog park and watch dogs interacting. Watch different body parts (ears, tails, eyes, lips, hair, overall posture) separately for a while. See if you can predict which body stances lead to which activities or outcomes.
Confidence/Fear
Signs of confidence: erect stance (standing tall), tail up, tail wagging in a slower sweep, ears pricked up or relaxed, direct look; relaxed, smaller pupils.
Signs of fear or concern: lowered stance, tail down or tucked under, tail wagging in a quick, frantic buzz; looking away or turning head away to look so that whites of eyes show ("whale eye"); dilated pupils. Dogs often bark out of fear, in an attempt to keep a distance between themselves and the Big Scary Thing, especially if they are cornered, fenced in, or on a leash.
Dogs that are aroused will often have their hair stand on end, usually the "hackles," the areas over the shoulders and just before the tail. This doesn't necessarily mean aggression, just that they are on high alert. Some dogs get "raised hackles" more easily than others; it's like some people who get red in the face very easily.
| This little puppy is looking confidently at the camera. His tail is up (due to his breed it curls over his back); he looks directly at us with no whites showing in his eyes, and his ears, though a little hard to see, are pricked forward. |