Regarding your one sheet, Rage.
Although I don't know the specifics of the alleged "very good" repros of this one, with most repros, the few things you want to look for are:
1. The size - if it's off by more than about 1/16" or so, that may raise a red flag.
2. The sharpness of the images and especially the text - if they're extremely fuzzy, like the Inception IMAX one sheet on MPC, that may raise a red flag. It looks like you even have a magnifying glass to check that, so that's cool.
3. The double-sided posters are generally easier to spot whether they're repros or not, for reasons mentioned on MPC and elsewhere, but this one was only made single-sided, so that doesn't apply to this one, of course.
4. The cropping, which on this one would be very difficult to tell since the white extends far in from the borders.
5. The colors - which can be very difficult to distinguish an original from a repro, unless they're side by side.
6. The paper - if it feels and smells right for the age of it - something you just know after seeing a lot of originals.
Frankly, I wouldn't worry about it. If most of the above look pretty good, then there's likely a high probability that it's an original.
Have fun at the party.
