It's super-easy. I run Emacs in daemon mode (start "emacs --daemon") but this isn't required; if you don't do that you need to start the Emacs server yourself in your ~/.emacs file, or run M-x start-server by hand.
Then if your system running Emacs is named "server", just run:
ssh -X server emacsclient -c
The -c tells Emacs to create a new graphical frame, and since you're using ssh it will forward the display securely back to your local desktop.