Play bowing is an invitation to play and a sign of happiness.
Direct eye contact means that a dog is feeling bold and confident. Casual eye contact means he's contented. An averted gaze means indifference. Dilated pupils indicate fear.
Pawing is an appeasing gesture. Licking another dog's face is an invitation to play or sign of deference.
Relaxed ears mean that a dog is calm. Erect ears show that a dog is alert and attentive. Ears that are up and forward mean a dog is challenging or being assertive or aggressive. Ears that are laid back indicate that a dog is worried or scared.
Yawning may indicate anticipation or stress. It increases heart rate and blood flow to the brain. Filling the lungs with oxygen and removing carbon dioxide. In fact, it helps a dog energize his body and gathers his wits.