Sorry for skipping 3 of the 12 days, I'll make it up by posting 3 times tomorrow with 2 of the promised casting ones.
This post is about Guardians of the Galaxy. How can it work? Its not like the Avengers, as the characters are not as well known and thus need no real buildup. So the best way to introduce them would be like in Serenity, a Whedon film which I found okay. Even though Serenity was the sequel to Firefly, you didn't need to watch that to watch this film. So basically, you shouldn't need the Avengers for Guardians.