Sort cell content alphabetically

Generally they are in alphabetical order. If they are custom fields they are in the order of the list, which the user can set to sort A-Z. They just need to refresh that sort if they add a new item to the list

As Graham mentioned, the sort A-Z does need to be refreshed. However once this has been done you can still move an item up or down the list. So if you have an "N/A" you can always move it back up to the top.