What would you consider to be something only a TRUE Lord of the Rings fan would know?

I wouldn't label a fan by what/how much (s)he already knows, but what their attitude on the fandom/story/characters, is.

As in, I consider a true fan; someone who's read the book, likes/loves it, and is interested in finding out more, and is learning more because of that interest. Even better if this fan also likes/loves discussing and debating the book/other fandom stuff. That's all that is needed for a true fan title, in my eyes.

A really, really old guy who lives in the old forest that saves the hobbits by being buried by the tree.

Knowing who the following people are:

Tom Bombadil
Glorfindel
Erkenbrand
Prince Imrahil
Ghan-buri-Ghan
Gildor

Feel free to add more to the list.

Knowing Who Gil-galad,
Turin Turambar,
Hurin,Barahir,Feanor,Manwe,Fingolfin,
and the Edain are

I would consider people a true fan if they could describe what were the Trees of Valior and also describe to me who is Melkor otherwise known as Morgoth.

Being able to talk about the sundering of the elves and name, or describe, all of the sub branches thereof. To be able to identify the series of events leading up to the forging of the rings of power. The true fan however, is more interested in the future of Middle earth and the possibilites that it contains. After all the third age wasn't the end (unless you're Noldor).

knowing what the Barrow-wights are, =)

I do now thing that there can ever be the #1 fan....I think that if you LOVE LOTR or like it in anyway, you are a cool person in my book lol

How long Frodo had the ring before setting out on his quest.

Before i watched the movies,i read the books and i was talking about tom Bombadil to my mom(she didn't read the books) because i thought he was in the movies.But she had no clue who he was so i had to explain it to her.

Ahahahaha, Tom Bombadil ^_^ I almost wet myself when I first read the book and he appeared, it was so funny. Because I had seen the movies at least 10 times each, but never read the book, so it was completely unexpected ^_^

he is the guy that sings to the trees