“I’m happy and relaxed.”
Total body position relaxed; relaxed hips, free movement, relaxed face
Open relaxed mouth
Tail at a neutral position (not too high or tucked between legs, unless that position is breed specific like high on a husky or tucked low on a greyhound or whippet).
“I’m alert and interested in something!”
Tail high that might be starting to curve over their back
Body erect with some tension
Ears erected or moved forward.
Mouth could be closed or still open
At this point, a dog is alert. This doesn’t mean they will be aggressive but a good sign for you to pay attention to your dog, what they are looking at and to the surrounding environment. Perhaps just getting their attention and if necessary calling them to you is all you need to do.
“I’m uncomfortable and anxious.”
Tail low and between legs
Ears back or flat against head
Sideways rolling eyes so that you can see the whites (“whale eyes”)
Yawning; Note, this is situation specific. True, dogs yawn when they are tired. They also yawn as a way to self soothe if they are in a stressful situation.
Showing normal behaviors that are out of context such as sniffing around in an unfocused manner, scratching if they are not itchy, biting at their own paws or other body parts, licking their nose or jaw when food is not present, shaking like they are wet when they are not wet. The key to this is to note that these behaviors are out of context.