Dogs should avoid:

Chocolate(Dark chocolates) coz it is very concentrated in cocoa, some dogs can eat a bit of it but some, just a small nibble can cause a reaction and instand death. It contains caffeine, theobromine, or theophylline that can even cause heart failure.

Onions are worst! A dog will die from the lack of red blood cells. Garlic, 1cm per 10kg body weight is ok as garlic helps in flea and tick control.

Grapes, the toxicity comes from the skin and seeds, your dog will appear fine now but in the long run... it could lead to abnormal death.

Fried and salty foods: These are greasy, full or fat and sodium.
Dogs cannot take up large amounts of fat and sodium. Why? Coz it will cause a dog to have a fatty heart that cannot work properly, liver disease from the high content. Sodium(salt) doesn't cause a dog to drop fur, it causes a dog to have kidney stones and kidney disease.

Oranges causes a dog to pass watery stool if given a lot.

Human medication and vitamins can do more harm than good. Always consult a vet.

Dogs cannot take in large amount of fruits and veges also.

Bones, raw bones from lamb, beef and chicken are ok, as long RAW. Cooked bones splinter in the tummy, can get trapped in the throat and tear the linings of the stomach. Anyway, still best to avoid bones in the end lah cause if your dog is a swallower, then NO BONES AT ALL!!!!

Yups.... I read somewhere.... 1cm garlic per 10kg is the best.