■ In western fandoms (for example non-anime, western-created fandoms, like Star Wars etc.), the pairings are listed with a slash between them and in no particular order. Example: Obi Wan/Darth Vader.
■ In fandoms from japanese series on the other hand, the letter "x" is used to indicate a romantic (or also just sex etc.) relationship between two or more characters.
So if you want to indicate that the characters are together (consensually or not) in the fic, you can write "character A x character B", but if it's, say friendship or family or something, it would be "character A & character B" or "character A + character B" etc.
■ In fandoms from japanese series, the seme (top) is always listed first, and the uke (bottom) listed second.
It may not seem as important at first sight, but it's actually is very important, because that allows your readers to know who is doing what in the story, and to search for the fics with the pairing in the order they like.
(If your characters ar reversible, you simply write it both ways, such as "Kaname x Zero and Zero x Kaname" or "ZxK & KxZ" and so on.)
I see that people often list the pairings wrong on FFnet summaries etc., which sometimes leads to disapppointment if a reader thinks they've finally found a fic with so-and-so as uke, or as seme, and then it turns out it was just a mistake in the way the author listed the pairing.
So I thought I'd write this little blurb in hopes it would be useful to other VK fanfic authors.
■ Similarly, in japanese fandoms there's also a way to list a pairing when one character is in love with the other but the other doesn't loves them back.
An arrow is used between the character's names, to show the feelings that are not returned.
Example: Aidou → Kaname. Or Luca → Kaname.
If you want to write a fic in which Luca loves Kaname but Kaname loves Yuuki, who is with him, you'd put in your summary: "Luca → Kaname x Yuuki".
This is less important than the rule of the seme first x uke second, which is the one that causes most confusion if they're listed the wrong way.
Subject: Your Japanese Additions! 
