Not an easy problem to solve, but I think a major factor in people choosing to go to the ER is the lack of/overcrowded walk in clinics, limited hours, and people who do not have a GP, either by choice, location, or because none in the area are accepting new patients.
More money needs to be spent in primary/community care to address these needs, and to change the culture of people going to the emergency room for non-emergencies. Public health teaching should be done to help people tell the difference.
I don't agree with charging people for coming to the ER for minor issues because that could deter some people from going when they have real problems. Perhaps like others have mentioned, having a clinic right by/across from a hospital that people can be sent to if they have been triaged and found to have a minor issue.