When it comes to fiction writing, creating believable characters is by far the most difficult. Sometimes it helps to sit down and write a list of attributes for all your main characters, or write a quick short story about each character that shows who they are through their actions. Remember, nobody is perfect, and with that in mind, you need to set out to make your characters multi-dimensional.
All novels have a central theme, and the main character is usually faced with a life-bending conflict, which eventually gets resolved for better or worse. If your main character is a strong, independent woman, show her weaknesses as well. She may be strong and independent, but perhaps that's a byproduct of fear of abandonment.
Your characters must be complex and interesting. The best way to bring out all their dimensions is to show them in action. And remember—emote, not describe. This sounds simple enough, but to really get down at the heart of who your characters really are is to look deep inside yourself and create your characters with honesty. Don't hold back. Dig deep into your psyche, and your characters will come alive in your head, and then let them take control over the story and their actions.
You may control the plot, but there will be plenty of interesting twists if your characters are living, breathing people who you put down on the page. Your characters are real, so let them live. They are human (or superhuman) with strengths and flaws. Show the good, the bad, and the totally ridiculous.
Dig deep. Tap into your most primal emotions, and then breath that into your characters as you create them, and they will become flesh and blood in their own images. Eventually your characters will become your best friends.
Love to all!