A golden retriever needs a bath whenever its coat is dirty, greasy or matted. Frequent bathing isn't necessary unless the dog stays outside and has frequent buildup of dirt or grime on the coat or skin. Too much bathing can cause the skin to dry out, which can lead to dandruff or itchy skin.
It's a good idea to brush a golden retriever before bathing. The long fur of the golden can mat easily, and getting the hair wet will only lead to tangles and larger matted areas. Removing loose hair and untangling mats before bathing will make the bathing and grooming process easier for the dog and owner.