A lot of people are unaware of the correct amount their dog should be eating. It is very easy for us to over feed if our furry friends come begging wanting more food or a treat. The best way to start to make sure that you are feeding your dog the correct amount of looking at the label on their food bag. It typically is broke down by size or weight of dog and then how many cups to go with that associated weight. These number of cups are for a full 24 hours. With that being said you need to evenly divide it up for the whole day. Most adult dogs should eat two times a day and puppies should be 3 times a day.
If you are changing what kind of food they are eating make sure you do it gradually. This process should be done over a week or more period of time. Start by only mixing a little of the new food in with the old food for a day or two then continuing adding more or the new and less of the old until the dog is only eating the new food. Doing it as a gradual process minimizes the chances of the dogs stomach getting upset.
P.S. Remember people food from the table is NO good for your dog.