That was so totally awesome!
Many roleplayers suffer from a problem where we see something in a movie we liked, and we want to play a character like that in WoW too, so we go ahead and try to mould our character into the vision from our mind.
But the problem is that we don't know anything about what being those characters in the movie is really like. Perhaps it was a vampire, or a king, or a seductive temptress, or a messianic savior of the human race - all these things are things we are not. Therefore we will probably play these characters badly. A roleplayer needs to draw on his or her own real experience in order to make a character work, no matter who that character is.
From my point of view
I was once just roleplaying for fun with a friend of mine, and we each created a random human character just for fun. I happened to create a female warlock, and as I was walking around, I realized I had no idea what it would really be like to be an evil summoner of demons. Eventually, we ran into this guy who was playing a nasty scoundrel of a man, and he started interacting with us. I didn't have much time, so I spontaneously came up with a silly idea: my warlock was not really a human at all, but a succubus cast out of the Burning Legion. Normally, this would be a bad idea, and I wouldn't recommend it to anyone, but at the time I felt it could work because I put a twist on it to try and make it funny. She was a dropout from succubus school, to whom the whole "evil temptress" thing just didn't come naturally at all. She kept on putting her foot in her mouth whenever she tried to say something sexy or tempting, and totally spoiled the effect.
Now, there are lore problems with this character idea, I know; and some of you may feel like no matter what, such a character is unforgivably Mary Suey. My point in bringing it up, however, is that the twist I put on her changed her from something completely alien to my experience into someone I could understand pretty well. I don't know the first thing about being a seductress - I've certainly never tried to seduce anyone in my life, least of all as a woman seducing a man! But I have made lots of social mistakes, created awkward situations, said exactly the wrong thing at the wrong time, and generally made a fool of myself, all without knowing what I was doing until it was far too late.
This solid experiential knowledge I have enabled me to relate to the character well enough that my friend and I could have a really fun time with this guy and the other random roleplayers we met that evening. The lore complications mean this idea wouldn't necessarily work out in the long term without some pretty open-minded friends to roleplay with, but the main idea is interesting: Can there be such a thing as an innocent demon? (Or an innocent warlock for that matter?) If a traditionally evil archetype were rather naive, could he or she accidentally escape the corrupting influences that should normally make him or her wicked to the bone? All these are questions I'd like to explore in a more plausible way.
From your point of view
For another player, however, innocence and naiveté may not at all define what you are interested in. Perhaps if you enjoy skydiving, bungee jumping, white-water rafting, or other such adventurous activities, then you could really relate to a character who likes to take risks and try new things every day, whatever the cost to himself. Or perhaps you had the experience of some kind of deep loss as a child, and so your character can be a kind of internal meditation on fear of abandonment.
Whatever you choose, your character should be a reflection of the kinds of things you really want to think about and understand, not an imitation of something you read in a book once. That's not to say you can't borrow details here and there, but the core of your character has to be something you can really relate to and enjoy.
As a matter of fact, actors have to go through a similar process when they begin to portray their character on screen. Anthony Hopkins is certainly nothing like Hannibal Lecter in real life, and yet when he portrays Hannibal in the movies, he must find things he likes and relates to in that character, so much so that he can really see the world from Hannibal's point of view, if he tries to. Without this sort of switching places, his portrayal of the character would never be convincing.
Likewise when a writer chooses to write about something, or a roleplayer decides what his or her character should say or do, he needs to be sure that those words come from within his or her own heart, mind, and actual experience, no matter how unlike the player's character is.