Step 1 - What is the dog doing? (Name the exact behavior the dog is doing, being careful to stay away from adjectives and descriptors. You're looking for a specific behavior.) Answer: Growling.
Step 2 - What is the dog's body language? (Observe the dog and list exactly what you see and hear.) Sally licks her lips and yawns. Her ears are back, she’s pulling away from people and dogs who come near, and her tail is tucked. Then when the German Shepherd comes in for a sniff, Sally tenses up more, her weight shifts towards him, she bares her teeth, her ears raise, and she growls.
Step 3 - What is going on? (Describe the context of the situation.) Packed reception area at the vet. Many dogs coming and going through the door next to your seat.