Are you more of a plot-driven storyteller or a character-based one? For me, it's always about the characters. What motivates them? Are they believable? What are they up against? I want someone to cheer for, and someone to despise in the novel-verse. I pick up a book already wanting to care about what happens to our heroine. Why? Because it's fun to live in someone else's shoes for a bit. So what makes a strong character?
The Flaw: Internal and External
Every person I know has one, and so should your character. Why? Have you ever read a story/watched a movie where the characters were just plain flat? They didn't have any sense of depth to them. They smiled waaaaaaay too much and never seemed to lose their cool? People aren't perfect, and when characters are they come across as boring. So, really put some thought into your character's flaw. Keep in mind that you should have an internal flaw (or secret) and an external flaw preventing our protagonist from crossing the finish line. Make the flaws meaningful so that when your character figures out what they want, their flaw prevents them from getting it too easily.
Just like the flaw, people are full of quirky things that make them interesting. Your characters should have them too. What do they do when no one is looking? What do they do that embarrasses them? These are the details that help your MC (main character) worm their way into our hearts. Think about the things that real-life people do that you find endearing, then attach it to a character and see if it works.
What, exactly, do they want? Why do they want it? Can you make that motivation more tailored to your MC and their novel-verse? For example, if you're writing about a pirate (and who doesn't love a good pirate?), does he want treasure like every other pirate? If so, how can we tailor the treasure-seeking motivation to our pirate? What if his treasure isn't money, jewels, or gold? What if the treasure this pirate wants, is a person named Treasure? What does he want with this person? Why is he willing to sail the seven seas to find them?
What kind of character traits catch your eye? Tell me in the comments below.