Leaning slightly forward, with ears pointed forward and up.

Stiff, slow movements that include the tail held high.

Long stares and refusal to break eye contact first.

Growling from deep withing the body as opposed to a throat growl.

Showing teeth.

Hair on back standing up.

Culing lip. 

Attempting to mount another dog.

Attempting to mount people/legs

Biting or snapping at the air.

Snapping or snarling when being petted, groomed or lifted.

Severe attacks on other animals such as cats or livestock.

Frequent attempts to chase moving objects such as bicycles, skateboards, cars and trucks.

Lunging.

Blocking your path.

Stiff facial expression.

Flattened ears.

General stiffness.

Raised hackles.

Straining against the leash to reach the other animal.