How do you make a lifelike character? Say hello to Mia, one of my characters.
I don't have a picture of her, but that's just as well, because you can't merely describe "what they look like" and call it good. People are more than their appearance and so are good characters.
Start with where the character is now, what (s)he is doing here. This can be as basic or elaborate as you like: Mia is a native of New Jersey with one foot in the "real world" and one in the supernatural.
Now you make up a character. Make him up right now. Call him Jacob. What's his deal? What is he doing? Is he a family man? An sorcerer? A punked-out waif?
So what is Jacob's conflict? Every character needs a conflict, whether it's a kid's book about learning to tie your shoe, or an epic trilogy about trying to destroy the ring which is the source of all evil. Mia's conflict involves trying to sort out what is truly real while at the same time helping her troubled best friend, Geival.
After Where They Are Now, you must decide how they got there. You cannot have a future without a past. Mia has a lot of past. The great thing is that there is no need to describe all of it. The point of knowing a character's past is so that you know why they are the way they are and can write them more realistically, NOT so that you can bore readers with an interminable backstory. Describe only as much past as is relevant to the story.
Where has Jacob been?
Next, I like to decide good points and flaws. Flaws are just as important if nor more so than the character's assets, because nothing makes someone seem more human than a few quirks. Mia has many faults. She is stubborn, has a temper, and tends to be a little snobby. Her good points are that she is more compassionate than she likes to admit and she is fiercely loyal to her friends. She thinks of the few people she likes as brothers (and sisters) and would do anything for them.
So ask youself, what are Jacob's flaws? His good points?
While we're on this subject, let's talk about a common mistake when writing fan-fiction. I'm not a big writer of that genre, but those who are tend to write a character who is, in fact themselves. That's fine. Fan-fiction is supposed to be fun, and what is more fun than putting yourself in a world you enjoy reading about?
The problem comes when you want "your" character to have every power and not only that, but be really good at it all.
A woman I used to know wrote Harry Potter fanfiction. "Her" character was called Natoria. Now, Natoria was the daughter of Voldemort, Dark Lord of Whatever, and Natoria inherited all of his powers. In fact, she teaches Defense Against the Dark Arts at Hogwart's, easily surpassing every other interviewee for the job. In addition, she is a Zim (I think this means she's telepathic), a parselmouth (that means she can talk to snakes) and a superstar quidditch player. She is romantically involved with Snape (as most female Harry Potter fanfiction characters are), the Weasley brothers have crushes on her, and she made straight As in all her classes as a student. With all this on her side, Natoria is calm even in the face of the worst that the Harry Potter universe can dish out. She acts with perfect poise, is always unselfish, and works toward the good of her friends.
Another of my friends has created his own version of Neverland (not the one in California) and a main character named Cubby. Cubby is one of the Lost Boys. Like the rest of the Lost Boys, he dresses in an animal pelt. He isn't the best tracker... in fact, he is more likely to trip over his own tail than to sneak up on anything. Cubby falls out of trees a lot, but laughs at himself when he reaches the bottom. He is the biggest Lost Boy: the one with red hair, chubby cheeks, and freckles. If he gets angry enough, he is a formiddable fighter, but most of his time fighting trolls or pirates is spent in terrified anticipation of being hurt. He often wanders off by himself to ponder about the existance of Neverland and to make wishes on stars.
Who would you rather read about? If you want to read about Cubby, click here.
When you've decided on a past, a present, and a personality, you can decide how your character will react to events and what will happen as a result, and the best thing of all is that these things will make sense both to you and your readers.
More than likely, you'll have several characters in your story. It's exceedingly important to balance them off of eachother and decide how they will interact. You might really like tragic poet-characters tormented by existential woe, but it is best to have a variety of personalities or else your story will end up looking like Monty Python's "Asylum for Overactors" sketch.
So pick three different personalities. Now how do they play out? The three main characters in the anime series Neon Genesis Evangelion are balanced perfectly. They are completely different, yet each is fascinating.
Shinji Akari is a shy, and somewhat cowardly. He pilots and Evangelion because he is told to, but posesses deep reserves of strength.
Asuka Langley Suryu is a beautiful but domineering girl-- a real Type A personality. She has to be the best at everything she does, and usually accomplishes this by putting others down. She only does it for fear that she'll never be good enough.
Rei Ayanami, on the other hand, is even quieter than Shinji. She is paradoxically the most powerful Evangelion pilot of the three, yet gets the most unimportant assignments because Shinji and Asuka usually fight over who gets the most important, dangrous jobs. Rei calmly and efficiently does what no one else feels like doing.
From a writing viewpoint, Rei provides a goad for the other two: when the fractious Asuka or trembling Shinji refuse to do something, Rei immediately says that she will. Asuka and Shinji refuse to allow themselves to be replaced. This is an excellent device for snapping naughty characters back into line without a lot of tediously-written argument.
Asuka provides an excellent contrast to Shinji. Without her, Shinji would sit in his own little world, afraid to speak up. Asuka irritates him so much that he has to come out of his shell and push back. Each of these characters needs the others to make the story interesting.
It is sometimes interesting to set up character relationships based on an existing format. Many novels do this by basing several generations of a rich family in modern times, off of several generations of a royal family from England's history. Even Mia, Geival and their friend Willie are loosely based on the weird relationship between the states of New York, New Jersey, and Delaware.