Originally Posted by
MSPeconomist
With separate tickets, it's useful to carry printouts (hard copies) of both ticket receipts and both PNRs. This is especially true if you want to check luggage through, but can help in IROPs too.
I would second this. Having printed copies has saved me multiple times when things have gone wrong (most notably when a schedule changed forced a reticketing and DL issued the new ticket as a ow rather than rt). Even when I'm not doing anything like separate tickets, I have all of the info in my bag.