When registering fb achievements, do I have to register them every time a new player hits the app or just once while developing? In examples they always show you registering the achievement directly before you post it but I'm guessing this is because they want the example to function properly but it has left me somewhat confused. Thanks!
You only need to register the achievement URL once, then when granting that achievement to a user you make a POST to /USER_ID/achievements?achievement=ACHIEVEMENT_URL&access_token=APP_ACCESS_TOKEN
https://developers.facebook.com/docs/achievements/ has more information