Love YOUNG FRANKENSTEIN. Here's the video link for the big number. You're welcome.
One of the main ingredients for a successful novel is having a relatable character. Your MC may be a vampire/alien/werewolf/zombie/Greek god or just Susie next door. It doesn't matter. What is imperative is that whoever it is, she's someone the reader can identify with. So how do we do that? How do we take a monster and give them a normal teenage (if we're talking YA) voice?
The key word here is "normal". You have to think of your MC (and any other character for that matter) as a whole person. Someone with the same thoughts, feelings, needs, and wants as the rest of us. Okay, so he's a werewolf. Fine. Then he's a normal person with an "extra issue". Now I'm not trying to be politically correct here. We're not going to start calling paranormal creatures "supernaturally challenged" or anything. I just want you to make sure you understand each character HAS to be a whole person.
Why was TWILIGHT so popular? Vampires? Nope. IMHO it was the romance. The teen angst. Etc. Now I'm not here to debate the execution (I certainly have my own opinions) or to suggest sparkly, brooding, shirtless (though this never hurts) entities. It's been done. Obviously. What I am suggesting is that Ms. Meyer took feelings that are meaningful to real teens and magnified those by using certain complications and devices.
I don't have a list for you today. I can't hand you bullet points for this. There are so many posts out there on character development, heck I've done several and will probably continue to do so. Maybe you interview your characters and do worksheets. Maybe you make collages. Maybe you know where they grew up and what their favorite color is. IDK. But no matter what your process is, or how cool your idea is, I want you to promise me one thing.
Remember that your character is a person and not a personification.
When we get so wrapped up in plot and structure and style and original ideas, we can lose sight of the fact that writing is ALWAYS about the human condition. And when you do find that human voice and tell the story through that perspective, I guarantee your work will be vastly improved, no matter how beautiful your writing is otherwise. Filtering through character was one of my most popular posts. But to do that successfully, we have to first have a grasp on the character we're filtering through.