How should I arrange my restaurant?

You should arrange your restaurant however you find works best for you!

If you want to take a look at some great guides to help you get started check out:

General Layouts: http://forum.playfish.com/showthread.php?t=534672
General Layouts: http://forum.playfish.com/showthread.php?t=640164
Island Layouts: http://forum.playfish.com/showthread.php?t=545136