When I first started writing, I used checklists to create characters. You know the ones – they ask you for the name, height, birthday, favorite foods, favorite movies, hobbies, dislikes, etc. of each character. I would fill out one of those for each of my main characters. Then I would start writing, referring to the checklist every once in a while so that “Robyn ate [look down at checklist] hummus smeared on fresh pita”. It is not that these lists are not helpful but if you are in the zone and you are thrumming away, you should know your characters well enough not to pull yourself out of the zone, run your finger down a sheet of paper to find what your protagonist enjoys eating. They allow you to keep track of certain surface characteristics of your character but not the essence that is your character.
There are a couple of great ways to get to know your characters without using checklists, all of them through organic (rather than forced) ways. First, you can let the character marinate in your head for weeks before you jot a word. There are always voices in my head and I find the stories that seem to drop out of me are the ones when the characters been active in my head for weeks. I wait until I am about to burst then write out the story. I never need to pause and ask: “What is he/she like? What would he/she do next?”
Another way to help you with your characters is to write scenes. These scenes do not have to go into your story or novel, but they allow you to drop you character into situations that will help you understand your character better. How does your character react when he/she is rear-ended by a muscle-head in a truck? How does your character behave at a serious event, like a funeral? Does your character’s interior thoughts match what comes out of their mouths? If so, what does that tell you about your character? What if it does not match?
Sometimes, you just need to write the entire story or a significant portion of the novel to fully understand your characters. The key is to make sure you know why your characters like or dislike certain things. It is one thing to list your character as hating Chinese food. It is another to show that when your character was a teenager, his/her mother worked three jobs and brought home Chinese food every night for dinner and now that your character is an adult, she gets nauseous when she smells egg rolls or fried rice.
Use your lists as a reference point (and not as an organic point) for your characters.