using (ServiceProxy proxy = new ServiceProxy(""))
{
  string s = proxy.HelloIndigo();
}

Besides its relative simplicity, another slant in favor of using the proxy generated for your service is that its base class implements IDisposable, therefore you can use the using statement to expedite cleanup of channel resources.

There are probably cases where you will need to interact with the channel directly, though none come to mind at the moment...for the most part you should be able to configure the channel using binding configurations.