If you want to save it like a cookie ( i.e user preferences ) , you should look into "SharedObject"
You could make a settings.xml file , and store it there. When the app loads , you parse and read the xml settings accordinly.
Can you just use a cookie? or are cookies mainly a HTML thing...
One thing I left out, we will need to store the data in a database. Don't think you can save the SharedObject in a DB.
Then make a settings class , and create an instance during runtime if one doesn't exist in your db. When a setting changes , record the change on your object and serialize it out to an AMF-capable backend. There you shove the settings object into your db through an ORM layer. When the user starts up the app again , send out their settings object and go from there.