I can't tell you what order they go in, but generally speaking, you would use the typical First Name, Last Name, etc order of things. If you take the record with the most amount of data and put that in a text file named 'test.csv' and import it without any field names, Address Book will show you a screen where you can choose which field names you want those pieces of data assigned to, and from that you can create the field names in your actual CSV file and then import it.
Keep in mind that CSV has a very specific syntax it's expecting, so if you don't conform you data to it, you won't get the results you want. You can read it here:
CSV Syntax
Mulder