Originally Posted by
godlovesugly
Also, if for some reason you need to get credit for miles after flights on partner airlines, keep your boarding pass and other information, because often you are required to provide fairly detailed information including your seat assignment.
Some airlines even require you to submit the original boarding pass for retroactive credit, to provide them with some protection against your requesting and receiving credit in more than one program. (At least one such airline with which I'm familiar is reasonable about enforcing that rule, though.)