It's different in every situation.  At the very least, you need these fields:

It really depends on how accurately you can set your defaults for other fields (not always possible), whether you use miscellaneous charges, taxes, optional fields, serial numbers, etc.  You can build separate .csv files for Orders vs Order_Details, using these fields, or build a single .csv file by adding "RECTYPE" to each row of headers (both header rows go at the top), where a Rectype of 1=Orders and 2 =Order_Details on the data lines.  Or you could try exporting just these fields to get started, and then add the other info you need.

It's different in every situation.  At the very least, you need these fields:

It really depends on how accurately you can set your defaults for other fields (not always possible), whether you use miscellaneous charges, taxes, optional fields, serial numbers, etc.  You can build separate .csv files for Orders vs Order_Details, using these fields, or build a single .csv file by adding "RECTYPE" to each row of headers (both header rows go at the top), where a Rectype of 1=Orders and 2 =Order_Details on the data lines.  Or you could try exporting just these fields to get started, and then add the other info you need.