Command-S: Save -- i.e. bring up the Save dialog
Command-O: Open -- i.e. bring up the Restore dialog
Command-Q: Quit -- i.e. just Quit -- prompt for a save first. Kind of like if I chose Exit from the ESC menu, except you should quit the program not go to the main menu
Supporting those three shortcuts is really a must for a Mac app.
Thanks for building it for the Mac in the first place -- just trying to help you get in good with the natives.

-Jason