Just thought I'd add to this, that other than a shock not fitting one way, when in doubt I go by the decal. Like BR549 mentioned in his post too.
Bilistein tends to orient their decals in the direction they want, or expect you might want to mount them. So if the name reads correctly with the body up, that's a good way to mount it. Same for the rod/boot up orientation.
If for no other reason than they look better that way. ;D
I've seen them either way, with different model shocks. So that seems to be a good way to judge when you're not able to get ahold of someone before installing them.
I've told customers either way over the phone, but sometimes forget to mention the label orientation.
Paul