Everyone forms a story differently. Some people start with an idea and form an outline. I do not do this. My creative process allows the character to drive the story. I have an idea for the story, but I like to get to know my characters most of all. Only after I know them can I truly understand where they are going, what they are doing, why they are doing it, how they will get there, and how they will react in certain situations.
Brainstorms sessions help. Meditate on the character in whatever way you can. Draw them. Write down all of their features. The reader does not need to see this, but you need to know the character inside and out for them to become and seem real. They don’t just seem real, they are real! They exist in your mind, and it is your job to write their story. Do it for whatever reason you want. I do it because if I don’t, they don’t stop nagging at me.
Once you know what they look like, consider why they look the way they do. Do they have a scar from a dog bite as a child? Freckles? Where does their family come from? What is their culture? Where did they go to school? This all has to be considered. Most of it will not be in the actual work, but you need it. Consider every angle, and don’t skip this process. Knowing your characters is vital. The story might be great, but if they characters aren’t real, if the reader doesn’t care about them, you have nothing but a plot.
A solid exercise for getting to know your characters is to write a short story about them. Place them in the strangest place you can imagine and then let them guide you. Write several short stories in many different places with different people and scenarios. What do they say? How do they view this world? Are they brave or do they cower? Do they speak their mind or are they more introverted? Explore. Explore. Explore.
The characters in your novel aren’t just made up people on the page. They are real. They have a breath, a life. Find out who they are, and let them tell your their stories.
If you want, you can publish their short stories as a teaser to your novel. Seeing something of what is to come before hand can be a positive thing. Any way that you can market will help you. If you can get someone to care about your character before they even pick up your novel, you have them hooked.