One of the first things I do when I sit down to start working on a Shiny New Idea is to figure out who I'm writing about. Characterization is a huge part of your story -- no matter how cool your high-speed train-chase scene is, nobody's going to connect to it if they don't care about the characters involved. That doesn't mean your character has to be the good guy (there are plenty of great novels told from the POV of antiheros and antagonsits), but they need to be interesting. More importantly, they need to feel like a real person. After all, one of the best parts of reading is watching the world through someone else's eyes.
So how do you make the imaginary characters floating around your brain into real people? One great trick is to start with a character sheet.
Character sheets can be as detailed and in-depth as you want. Some people prefer to stick to a few defining characteristics, but I really like to go whole-hog when I'm building new characters. Not everything on you character sheet can or will wind up in your final draft (you don't want to info-dump about Jimmy's favorite color or how much he loves bubble baths if it's not relevant to the story you're telling), but when you, as an author, know these things about your characters, it makes it easier to write about them like you're writing about a real person.
If it helps, think of your characters like icebergs (only, not like icebergs that you spot from the prow of your ship. Those kind of icebergs are bad. Very bad. Trust us). What readers see on the surface is only a very small percentage of what you know about your character's history, personality, likes, dislikes, hopes and dreams, etc.
Since I like to really plumb the depths of those icebergs, I work with a very detailed character sheet. Full disclosure, I found this somewhere in the mires of the interwebz back in 2010, and I cannot for the life of me figure out where. So I can't take credit for the full OCD-ness of this sheet. But I thought I'd share my version with you, in case you're looking for a starting point for your own.
You should be able to download that if I worked Google Drive right (huzzah for Google Drive), but if not, the basics you want to include on most character sheets are:
Character's Full Name (along with any nicknames)
Character's Age/Gender/Race/Orientation, etc.
Physical Description -- height, weight, hair and eye color, any tattoos or scars, anything you want to add so you can picture them in your head
That last one can be tricky, but usually their political views, religious views, eating/smoking/drinking habits, temperament, pet peeves, sense of humor, self-image, and any fears and phobias they may have can give you a good indication of what kind of person your character is. Another good trick is to take the Meyers-Briggs personality test as your character
to find out more about how they'd likely behave.
The other key thing to note, somewhere on your character sheet, is your characters goal or dream. What does s/he want from life? What drives him/her forward in the story? That's going to be key in developing your plot too.
There are other questions you can ask yourself about the character to form ideas about what s/he will do in the story, such as how this character is different from others in the story, or what you like and dislike about the character. Feel free to add more if you think of them, or to delete some of the suggestions on that character sheet that you don't feel you need to know (maybe you don't care why your character got her bellybutton pierced, and you'd rather take notes of what pets s/he had growing up or where all s/he has lived in the past). This is just a template to get you started. Fill it out for just your main character, or all of your characters, or just the bad guy -- whatever floats your boat (or pirate ship)!
Do any of you use character sheets? Are there characteristics or questions you have on yours that I didn't include? Let me know in the comments!