I think it primarily depends on the hypervisor you're using. For example, if you use OpenVZ, you may use: vzctl *veid* enter to enter into the console.
About nova get-serial-console, you should take a look there: http://blog.oddbit.com/2014/12/22/accessing-the-serial-console-of-your-nova-servers/. There're also nova get-rdp-console, nova get-spice-console and nova get-vnc-console.