Here at my journal I've made a post with suggestions on how to nominate multimedia fandoms (fandoms that exist in multiple forms, such as a comic and a movie, or a book, a TV miniseries, and a movie) so that you don't accidentally nominate the comic when you wanted the movie, or whatever.
I should stress that my post is UNOFFICIAL. I'm a tag wrangler on the AO3, so I have some knowledge of how the tags work, but my post is just my suggestions, not an official communication from the Yuletide mods or An Archive of Our Own. I wrote it up because I noticed the official "how to nominate" tutorial doesn't deal with this issue, and I think it's kind of important.