1. Does the hair coat feel greasy? Is the skin colour a normal gray-white or is it pink or red with inflammation? Do you see dandruff-like scales of dead skin among the hairs?
2. Use your fingers to brush the hair against the grain. Do you see numerous little black specks? These are excreta of fleas.
3. Now smell your finger. If the ord0r they picked up is rancid, rank or fishy, its a sign of poor health.
4. As you examine the eyes check for matter in the corners. Pull down the lower eyelids so you can see the underside. Are the lids red inside or irritated on the edges?
5. Look into the ear holes. Do you see a lot of wax? Do the inside look oily? Sniff to check for an offensive odor.
6. Inspect the gums fir a red line along the roots of the teeth. To check the back teeth for that red line, raise the upper lip and push back the corners of hte lips at the same time. (It is not necessary tp open the mouth.)
7. Now check the teeth themselves, including the back ones. Are they gleaming white or coated with brown deposit? Does the breath smell okay or are you overcome by it?
8. Last, feel the backbone in the middle of the back and run back and forth (sideways) over it. Do you feel definite bones there? Is there a prominent ridge sticking up in the middle? if your answers to these questions are yes, your animal is much too thin.
Source from Dr. Pitcairn's Complete Guide To Natural Health For Dogs And Cats