If a patient has a low ceruloplasmin with normal 24 hours urine copper excretion, how would you go about an approach to evaluation of other disorders of copper metabolism as a cause of liver disease?

It depends on how low the ceruloplasmin is. If the level is undetectable, I would be worried that the 24hr urine result is spurious. In this case, I would repeat the studies, evaluate for KF rings, and consider genetic testing based on how concerned you are for Wilson disease (i.e., family history, ...