Change Level over Network, Whats the corretct way?

Hi, I'm trying to learn unity rpc calls to a simple multiplay game.

[Detailed]:
> I made a second scene(level);
>The server changed the scene before client connect;
>>>> When client join the server he connect in first scene because he don't got the change scene call.
Made a LOBBY Layer before the "Real Game";
>Wait people connect to server;
>Did a change level via RPC call;
Its ok, it change the level to everyone, BUT?
..
If someone join the lobby after the "change the stage rpc call", he...

Change Level over Network, Whats the corretct way?