Eyes are clean without eye discharge, coat is shiny, the dog is lively and active.
There are several points to note when choosing a dog. Hearing: When selecting a puppy, the first thing you should do is place it in a stable place, then snap your fingers at its side or back of the head. If the puppy responds by actively looking and searching toward the sound source, it indicates normal hearing.
Nose: A healthy dog's nose is moist (a dog's nose may be dry just after waking up), and the nasal discharge is clear and transparent mucus.
Eyes: During selection, you can place the dog in a somewhat elevated place and wave your hand in front of its eyes. If it shows fear but does not jump down and its gaze follows your hand movement, it shows normal vision.
Body too thin
Reasons for a dog being too thin include insufficient food intake, parasites, internal diseases, and sudden changes in environment which can cause weight loss.
Abnormal stool
Frequency, shape, color, and smell of stool all reflect health status. Diarrhea is usually caused by overeating leading to indigestion. If stool contains blood, there may be parasites.
Additionally, constipation may indicate organ problems or fractures.
Abnormal urine
Normal urine is light yellow. Dark or milky urine may indicate kidney disease. Difficulty urinating may mean urethral obstruction.
Abnormal eyes
If eyes are congested, cloudy, sensitive to strong light, or swollen, mild cases may be caused by foreign body irritation, or diseases such as infectious viruses, injury, vitamin B deficiency, eyelash inversion. Severe cases might be keratitis, chronic conjunctivitis, hepatitis, etc.
Nasal abnormalities
A healthy dog's nose is moist, black, and glossy. If your dog has excessive nasal discharge, nosebleeds, nasal congestion, or swelling and cracking of the nose, it may have a cold or rhinitis.
Purchasing a dog is an experience many pet lovers share, but how can you buy a healthy and lovely dog? The most important thing is to follow the "Five Checks".
First check expression: The mental state reflects neurological function and overall health. A healthy dog has bright eyes, alert ears and tail, reacts quickly when approached, showing willingness to approach or avoid. Dull eyes and depressed spirit indicate possible illness.
Second check overall condition: Observe if the dog moves flexibly, walks steadily, has clean and smooth fur, well-developed muscles, symmetrical and strong limbs, no limping.
If there are obvious scars, scabs, hair loss, or small bumps on the body surface, it indicates current or past skin diseases (such as mange, demodectic mange, fungal infection, etc.).
Third check eyes: Healthy dogs have bright, lively eyes, clean and neat eyelashes, with slightly moist eye rims. Many diseases show signs in the eyes. Conjunctival congestion and redness are signs of infectious or febrile diseases.
Yellowing of conjunctiva (pale yellow) suggests possible liver lesions. Pale conjunctiva often indicates anemia caused by various reasons. If the cornea (outer layer of the eye) is cloudy or has white spots, it may be late-stage canine distemper or simple keratitis; a bluish-gray cornea might indicate infectious hepatitis (clinically known as "hepatitic blue eye").
Excessive eye discharge is especially concerning, often seen in dogs with distemper or infectious hepatitis.
Fourth check nose: A healthy dog's nose tip and nostril areas are moist with a cool feeling. Dryness often indicates upper respiratory inflammation (usually caused by infectious or febrile diseases). If obvious watery, mucous, or purulent nasal discharge occurs, it reflects some infectious diseases (such as canine influenza, distemper, etc.).

Fifth check lower abdomen: First-time buyers or those unfamiliar with dogs often overlook this. If there is a obvious round bulge around the dog's navel or lower abdomen, it is likely hernia (umbilical or scrotal), generally requiring surgery.
If you follow these steps when buying a dog, combined with some basic dog knowledge, you will surely buy a lively, adorable, and satisfactory pet.