1. Take your OTP.
2. List your personal canon for those characters. So the stuff that has nothing whatsoever to do with the books, but in your head is irrefutably what would have happened.
Beware the insanely random order. I thought of these in a strange order and I didn't feel like continually rearranging them.
1. Neville and Luna are meant to be. Suck it, JK.
2. Luna's parents are named Orion and Estella. Think about it... Orion is a constellation and estrella is the Spanish word for "star." Fits with the name Luna pretty well, doesn't it? Orion and Estella Lovegood. Even if JK names them in (or after) DH , I don't think this would change for me.
2.5 Along those lines, Neville's parents' full names are Miles Franklin Longbottom and Alice Louise Pennyweather Longbottom. I have no idea where the maiden name "Pennyweather" came from, but I love it. I made Frank's name the way it is because I honestly cannot figure out how a woman named Augusta from a pureblood family could name her only child "Frank." "Miles" seems like a family name to me, something that every Longbottom man (except Neville) would share. None of them would be called by it, though. Augusta always called (and still calls) her son Franklin, but his friends at school and in the Order call him Frank.
3. Neville knows more magic than anyone, even he himself, thinks he does. Magic may not comes as easily to him as it does to certain students, and he definitely isn't brainy like Hermione, but he can hold his own. Once someone believes in him (Lupin in PoA comes to mind), he can do just as well as any other student. Having Luna around to believe in him helps him immensely. (And vice versa.) It'll probably take him a few tries to pass his Apparition test, though. *snerks* Maybe he'll even have to take the class again with all the 6th years.
4. Neville has a strong desire to travel. Having lived a very sheltered life under his grandmother, Neville can't wait to get out and see the world. He has never been outside the UK, but once he finishes school, he wants to change that. And he wants to take Luna with him when she finishes school. Luna, though she has traveled extensively with her father, cannot wait to travel with Neville.
5. Luna's eyes are blue. Call me crazy, but I love her with blue eyes. I always pictured her that way and, for a long time, I thought that's what actually canon stated. When I saw in the HP Lexicon that she had grey eyes, I think I did a double take. Now, I can't get my image of her to have grey eyes. It just ain't gonna happen. Evanna's not helping matters any. XD
6. Neville is a good dancer. The book says he "trod on Ginny's toes" (my paraphrase), but I prefer movie!Neville in this sense. Maybe in my world he becomes a good dancer after the Yule Ball, I dunno. All I know is I like him as a good dancer. However, he'd be a little lost in a disco. The waltz is more his thing.
7. Frank and Alice's possessions are in Gran's attic, and Neville likes to go up and look through them every now and then to learn about his parents' former lives. I don't think this one needs much further explanation.
8. Luna's mythical creatures are, actually, sometimes too far-fetched for Neville. But he would never tell her that. He finds it endearing, if a little strange, and he loves the level of faith she has. She, in turn, adores him all the more for the way he treats her about her beliefs. She can tell that he doesn't always agree with her, but she never feels patronized by him.
9. Upon meeting Orion, Neville finds, in a way, "the father he never had." As cheesy as it sounds, I think that Orion wants Neville to think of him as a father figure. Neville looks up to him as a strong man who lived through the hardship of his wife's death and has continued to raise Luna on his own. As Neville hasn't really had a role model for how to behave as a husband or father, he admires Orion and seeks to follow after his lead. You can bet your sweet bippy that Neville will ask Orion's permission to marry Luna when the time comes.
10. Gran doesn't like Luna. She's flighty, irresponsible, and immature in Augusta's eyes. The little bit of respect Augusta has for the girl comes from the courage she showed in the DoM and the battle at Hogwarts. But that does not make her good enough to be a Longbottom. Though Augusta know deep down that she no longer has much say over what Neville does with his life, she will make her displeasure known at every oppotunity. Neither Neville nor Luna care very much what she thinks. (Yes, my Neville has a backbone!)
11. They shared their first kiss in his sixth year. Here's where I really screw with canon. I like the idea of Neville and Luna being together during HBP. I haven't read the book in a while, so I could be stabbing canon in the back... BUT I DON'T CARE! On the first Hogsmeade trip of the year, Neville summons up his courage and kisses Luna in front of the Shrieking Shack...in the rain. Mmm...
12. Trevor is not nearly as important to Neville as he used to be. When Neville first started at Hogwarts, he was a fat, shy, loner with no friends. Trevor was the only one who was around (most of the time) for him. But, as Neville developed real friends, he had less and less need for Trevor. He was still a dear pet, and Neville still talks to him sometimes, but he has become more of a pet than a confidante and best friend. With Luna in his life, Neville doesn't have to rely on Trevor for companionship and love.