A stranger in a strange land
If you've ever clicked on my name while reading WoW Insider, you probably noticed that I actually live in China, so one of the experiences I'm extremely familiar with is that of being the foreigner. When you're a stranger in a strange land, there are a lot of ways in which you are forced to adapt under new limitations: language, accent, styles of communication, culture, habits, even food! All these can make life very difficult at first. You have to learn the language and culture of the people with whom you live if you're going to communicate and get along with them.
After I started playing WoW, I wondered what a foreigner to Azeroth might be like. When The Burning Crusade came out, the new draenei race seemed the perfect opportunity to explore some of my experiences as a foreigner. I had already been waiting for my chance to play a hunter, so I conceived of a draenei hunter who was a devoted follower of the Light, very much invested in her own traditions, and yet deeply fascinated by all things Azerothian -- people, animals, architecture, even the unique texture of mud or grass. The catch for her was that, at first, she could not speak Common. I have a direct experience of the language barrier through trying to learn Chinese while living in China, so I felt it was something I could roleplay pretty well. She could speak fluently in Draenei, of course, and another draenei could translate for her -- but whenever she spoke in Common in her early levels, she would have to carefully try out the words and very slowly learn what they mean. In the process of leveling to 70, she has learned Common pretty well by talking with common Azerothians. Since she received no formal training, she still has a very thick accent and makes lots of grammatical mistakes, but her way of speaking is adorable and engaging, and she just loves being able to speak her mind and understand her new friends.
A dream come true
Another idea I had for a new draenei character had to do with theater. Acting was my favorite activity in high school, but for various reasons, I never got to continue with it after I graduated. I may love acting, but I'm not exactly the next Sean Connery. For me roleplaying has been a way to express that sort of creativity, and I thought it would be interesting if I made a character who was an accomplished actor.
This is an example of how your character can be an expression of a personal fantasy you've always had, but for whatever reason never actually happened in real life. Many great character ideas come out of this sort of idea. We actually spend a lot of mental time thinking about these sort of fantasies, so we might know them quite well even if we don't have much actual experience in that area.
This character was also a draenei, but one who had had a chance to get familiar with Azeroth and Common much earlier, after the first Alliance expedition came through the Dark Portal into Draenor. I figured my character could often tell his friends about draenei plays he performed in, based on modern American films or even Shakespeare, and maybe even do a little performance for his friends now and then. As it turned out, he hit the jackpot and became a member of a theater-troupe guild, which regularly meets in the park to play improv acting games. He is the famous actor I used to wish I could be.
Avoid the Sephiroth Syndrome
One of the mistakes that people often make when starting out roleplaying is that they don't draw on their own lives for inspiration. Instead they draw only on the fantasy stories they enjoyed a lot when they were growing up. If someone doesn't outright name their character something like "Sephiroth" or "Legolas" or even "Morgana le Fay," they often base their own character on these previous characters to such an extent that it becomes cliche and other players get bored.
Also, if you bring in too much of Forgotten Realms or Lord of the Rings, or even your own made-up fantasy world into WoW, people will tend to reject it because it doesn't fit. You may have this great idea for how your paladin main character was turned into a vampire and forced to bear the demon child of a 100,000 year old dragon who then put his soul in the baby and sent her back in time so that she could grow up into your night elf hunter alt -- but there's nothing in that fantasy story that other people can relate to. You'll find most other roleplayers just say, "okaaaaay..." and just nod politely before drifting off to other activities.
That's not to say that you can't make up any fantasy of your own, but it should fill a gap left in Blizzard's story. They don't go out of their way to plug in all the holes in the lore, so there's plenty of room for you to be inventive and still true to the lore (especially if you satirize it). The most important thing, however, is to be true to human experience. Your character needs to be dealing with issues that we human beings are dealing with too: the loss of a friend, the discovery of something new, the thrill of overcoming a challenge, or even the innocence of being somewhat clueless.
Let your best qualities shine
Another mistake people often make is that they put all of their worst qualities into their character. They insist on expressing their "sarcastic wit" or "withdrawn melancholy," not realizing that antisocial qualities are hard for other people to enjoy. Of course a 100% perfect character is hard for people to enjoy too -- so the key here is balance. Whatever you do, you want a character that can interact with others in such a way that people want to interact with them again next time. Part of that means being genuinely likable in one way or another, and part of it means being flawed in some interesting way, but not so flawed that people would rather just target you and type /ignore. A sense of humor, if you have any at all, is a key asset, as well as an interest in other people's characters before as your own.
So the next time you you sit down to make a new character, think: What are some of your best qualities that other people enjoy? What are some of the experiences that taught you these qualities? Do you have any less-than-perfect qualities which nonetheless draw people to you rather than push them away? Who were some of your real life heroes growing up, people you admired but could not actually emulate in real life? How might you incorporate a childhood dream into your WoW character?
With a little bit of digging in the mine of your life, you may find people love being around your character just as much as they love being around you.