So you want to Create a Character?
It's best to start with the basics.
Remember, it's perfectly okay to change your characters' names as you write your story. A character's name could be as simple as a common name, such as Max Reuben, or could be as elaborate as Cecelia Jane Vivian Lily Iris Alexis Thompson. But remember, you want to have a name for your character that can be used conversationally. Max and other monosyllabic names are great, but for you more creative types, just make sure your character can have a nickname, or will just go by one of his or her many names.
Another thing to remember is that, as a writer, your goal is to please at least one person besides yourself. And you're audience isn't stupid. Don't just name a compassionate person a foreign word meaning pacifist or love. It's rather obvious. Same rules apply when you have character types with stereotypical names tacked on, such as a brutish guy named Butch.
Be Creative, but not blunt with the character's role in your story when naming.
This seems rather obvious, but is incredibly important. The age of a character does inherently affect the way your audience will perceive them. An older character, in later years, 55-ish to old enough to look like a walking corpse, will be perceived as a wise man. Middle-Aged characters, from 35-ish to 55-ish, will usually be given the role of mentor. Most main characters fall under the age range of 10 to 35-ish. As the age goes up, so does the age of the audience. It is easier for readers to relate to a character within their age group, such as a teenager trying to survive high school, or a secret agent working for the CIA.
The Age of characters undoubtedly will change the way your audience will undoubtedly make the audience look at them differently. Take for instance the teenage prodigal wizard, Harry Potter, and his wise mentor, Dumbledore. People like Dumbledore because of what he's done, but Harry is the character more people identify with, or his buddies Hermione and Ron. (Who happen to be around the same age as him, appealing to the same group of kids!)
Is your character a Guy or a Gal? Keep in mind that a reader most often identifies with a character of the same gender. So who is your Audience? A balanced ratio of Male to Female characters isn't always needed. Sometimes the guys will be more prevalent in your story than gals, and sometimes it's the complete opposite. If you want to create a character of the opposite gender but don't think you can get the personality right, ask a friend of the opposite gender. Most buddies should be willing to help you!
Now that we have the 2 most important factors determine Appearance sorted out, it seems appropriate that this is covered now.
Close your eyes, and imagine your character. Think of them as if they are a close friend, and you're talking face to face. When the image is solid enough, describe it. What is their hair colour? What about their eyes? What is their skin tone? How tall is s/he? How much does s/he weigh? Any scars? What about tattoos? Now that we have our base, we have to cover your character's wardrobe. What do they wear? Shoes or sandals? Shorts, slacks, or jeans? What does s/he wear for a top? Is it a bikini top (female only), or is it nothing (male only)? Is it a T-Shirt or a Sweatshirt? You decide.
Make sure than the appearance is solid, and that every inch of their body is described, either by basic physical information or by being covered by clothes. You want to create a description for your character that is short enough so that it keeps it simple, but long enough so the audience doesn't see him or her as a stick figure with a name hovering above their head.
A good character is one you, and the audience, identify with. And that depends not only on Age and Gender, but PRIMARILY on their personality. For simplicity's sake, however, we're making a character for a story. Events in the story will impact their personality, so we can just use basic information for this.
Are they shy?
Are they outgoing?
Give three positive attributes
Give three negative attributes
Don't be afraid to change any of this as time goes on! Things are constantly changing in the universe you've created for your character, and they change as you see fit!
This is something I've always had trouble with. Creating a back story for a character is essential. They aren't all babies! The history of your character helps influence their decisions. Did somebody die? Did s/he accidentally hurt someone with an action that may return in the story you're writing now? A history doesn't need to be long, but it should have at least three sentences for each year of age that a character has under the age of 12, two sentences for each year in their age (for teenagers to mid 30s), one sentence per year of age (everyone else). You should end up with roughly 50 to 150 sentences depending on how old your character is. This amount of personal history helps you further the depth of character your creation has, and helps you if you want to add in past references (having already told the past of your character, s/he can't have conflicting stories referencing their past, unless intended).
And that's it, enough information for the base of a character you want to write a story around!
Or, if you'd rather not, just make a name, face, and get to writing.
Imagination and creativity are main tenants of the writing universe, but don't forget to create a proper environment for your character!