Over the centuries wolves evolved an elaborate system of body language, facial expressions, and vocalizations to communicate with each other. Domestic dogs also use this means of communication, and all of these signals are easily understood by other dogs. If you can learn to interpret how your dog is feeling by observing its posture and expression and listening to it, you'll be well on the way to successful communication with your pet and better equipped to solve any behavior problems that arise.Following are some major canine attitudes and their typical outward manifestations.
AGGRESSIVE
	Ears	Forward or back, close to head.
	Eyes	Narrow or staring challengingly.
	Mouth/ Teeth	Lips open, drawn back to expose teeth bared in a snarl. Possible jaw snapping.
	Body	Tense. Upright. Hackles on neck up. Completely Dominant position.
	Tail	Straight out from body. Fluffed up.
	Vocali- zation	Snarl. Growl. Loud bark.
ALERT
	Ears	Perked-up. Turning to catch sounds.
	Eyes	Open normally or wide.
	Mouth/ Teeth	Mouth closed or slightly open with teeth covered.
	Body	Normal. Possibly standing on tiptoe. Slightly Dominant position.
	Tail	Up. Possibly wagging.
	Vocali- zation	None. Low whine or alarm bark.
ANXIOUS
	Ears	Partially back.
	Eyes	Slightly narrowed.
	Mouth/ Teeth	Mouth closed, or slightly open in a "grin."
	Body	Tense. Slightly lowered in a Submissive position.
	Tail	Partially lowered.
	Vocali- zation	Low whine or moaning-type bark.
CHASE, BEGINNING STAGE
	Ears	Perked-up, forward-pointing.
	Eyes	Wide open. Very alert.
	Mouth/ Teeth	Mouth slightly open. Excited panting.
	Body	Tense. Crouched low in a predatory position. Legs bent, poised to run.
	Tail	Extended straight out from body.
	Vocali- zation	None.
CURIOUS/EAGER/EXCITED
	Ears	Perked-up, forward-pointing.
	Eyes	Wide open.
	Mouth/ Teeth	Mouth open, teeth covered. Possible panting.
	Body	Normal stance. Possible wiggling, standing on tiptoe, or pacing.
	Tail	Up. Wagging.
	Vocali- zation	Excited short barking, whining.
DOMINANT
	Ears	Up straight or forward.
	Eyes	Wide open, staring.
	Mouth/ Teeth	Mouth closed or slightly open.
	Body	Very tall posture. Hackles may be up.
	Tail	Stiffened and fluffed. Up or straight out from body.
	Vocali- zation	Low, assertive growl or grunt.
FEARFUL
	Ears	Laid back flat and low on head.
	Eyes	Narrowed, averted. Possibly rolled back in head, whites showing.
	Mouth/ Teeth	Lips drawn back to expose teeth.
	Body	Tense. Crouched low in submissive position. Shivering, trembling. Possible secretion from anal scent glands.
	Tail	Down between legs.
	Vocali- zation	Low, worried yelp, whine, or growl.
FLIGHT, BEGINNING STAGE
	Ears	Back.
	Eyes	Wide open. Possibly rolled back with whites showing.
	Mouth/ Teeth	Slightly opened mouth. Possible drooling.
	Body	Tense. Shivering. Low, poised to run.
	Tail	Low or between legs.
	Vocali- zation	None. Possible yelp or whine.
FRIENDLY
	Ears	Perked-up.
	Eyes	Wide open. Alert look.
	Mouth/ Teeth	Relaxed, possibly slightly open, "smiling" mouth.
	Body	Normal posture. Still, or possible wiggling of whole rear end.
	Tail	Up or out from body. Wagging.
	Vocali- zation	Whimpering, yapping, or short, high bark.
GUARDING
	Ears	Perked-up. Forward.
	Eyes	Wide open, alert.
	Mouth/ Teeth	Mouth slightly open, teeth bared. Snapping or gnashing of teeth.
	Body	Tense. Rigid. Hackles up. Standing very tall in an aggressive or dominant stance.
	Tail	Rigid. Held straight out from body. Sometimes fluffed.
	Vocali- zation	Loud alert bark. Growl. Snarl.
PLAYFUL/HAPPY
	Ears	Perked-up and forward, or relaxed.
	Eyes	Wide open. Sparkly/merry-looking.
	Mouth/ Teeth	Mouth relaxed and slightly open, teeth covered. Excited panting.
	Body	Relaxed, or front end lowered, rear end up in the air, wiggling in a play-bow. Excited bouncing and jumping up and down. Circling around and running forward and back in an invitation to play.
	Tail	Wagging vigorously.
	Vocali- zation	Excited barking. Soft play-growling.
PREDATORY
	Ears	Alert. Held forward or backward to catch sounds.
	Eyes	Wide open. Staring, focusing.
	Mouth/ Teeth	Mouth closed.
	Body	Rigid. Low to ground, ready to spring forward. Quietly sniffing the air.
	Tail	Straight and low.
	Vocali- zation	None (so the prey won't be alerted).
SUBORDINATE (SUBMISSIVE)
	Ears	Down, flattened against head.
	Eyes	Narrowed to slits or wide open, whites showing.
	Mouth/ Teeth	Lips pulled way back from teeth in a "grin". Nuzzling or licking other animal or person on face.
	Body	Lowered to ground, front paw raised. Lying on back, belly up. Possible urine leaking/dribbling. Possible emptying of anal scent glands.
	Tail	Down, between legs.
	Vocali- zation	None, or low, worried whining. Possible yelping/whimpering in fear.

Refer : http://www.pawsacrossamerica.com/interpret.html