there are many things that are toxic to be aware of… onions, chocolate, and grapes are 3 examples. if you are ever in doubt, don't feed it. I stick to tried and true things - chicken, beef, fish, turkey, peanut butter, cream cheese, mozarella cheese, low fat plain yogurt, carrots...
be aware of the sugar and fat content in the foods, try to stick to all natural (less chemicals), and use sparingly. of course, if your dog exhibits any strange behavior (sign of allergy or intolerance) stop feeding these foods. (for example, my dog cannot tolerate any venison, he vomits)
again, moderation is key!!! human food, IMO, should not replace a dog's regular diet (unless the diet is a homecooked diet or raw) I primarily use human food to train my dog, and to fill his kong, otherwise he sticks to his regular diet of kibble, canned food, and dog biscuits.