Welcome to Gaia! ::

If your thinking of yaoi, I guess I could give topics. I'm not gonna spell out a story for you lol! That's bad for me to do as a fellow author.

For just a pairing - opposite pairings are fun. Your main character can be either of the two. Also, as a side joke you can add another character who likes to flirt with your main character just to put him on edge, or make him feel uncomfortable. It could be set at a private school to make it easier, or they can all be members of some organization, or job. You could have your main character really like the second character, or the other way around. This kind of format is the easiest to do for a fanfic because it's also easy to replace your characters with some of your favorite anime characters. ^^

For a triangle - Now this isn't like having that side character that flirts with your main or secondary character. This format is harder to write in my opinion, many authors I'm sure could disagree. Opposites are usually not a great idea for this one unless your talking about the two characters that like the third character. It's usually best to make the character who is being chased oblivious to the two. Like a Blind Joe as some authors like to call this character. The two chasing characters could be trying to knock out their opponent, or win thier goal first. If you want to create tension in later parts of the story, or just make things interesting, you could easily start everything as a dare between the two chasing characters.

Ok, I hope I was a little help. Just a little boost for ya lol! ^^