My characters drag me around by the hair. Which on the bright side means they have a personality all their own, and on the cloudy doom and gloom, rain during a picnic side means the characters have a personality all of their own. And sometimes, that personality sucks.
What To Do If Your Protagonist Is A Drag?
I was so determined not to fall into the blank slate, reader-insert main character. That's a protagonist who doesn't have much personality so that the reader can imagine themselves as the main character. It wasn't until I started writing that all my good intentions came undone. The problem is this: loud, personality-filled characters are exhausting. Exhausting to write and exhausting to read. A way around this is to have multiple POVs, but I automatically fall into third-person limited. It's my comfort zone. I couldn't stand my main character, she was noisy, opinionated, loud-mouthed, and she moaned way too much. I loved all the other characters, the ones who popped in, said something pithy, and then swanned out the door to much mental applause. When I actually considered writing the whole book from their point of view… well, that would have gotten boring quickly.
So What's The Workaround? Whether You're A Pantser Or A Plotter, Boring Characters Are Boring.
Let your character feed off other characters. There are many sides to a person, and the different people we surround ourselves with often bring out that different side. My main character loves a sarcastic aside, but she tones it down or gets systemically more sarcastic depending on who she's with. When she's around her pals, who are straightlaced and disapproving, she is at her maximum ridiculous- which is fun for me to write and keeps conversations flowing without getting too serious. She gets a bit more serious when she is around people who are sucking up all the whimsy from the room. She takes on the role of the serious one. If anything, she gets annoyed by the same asides she would have uttered herself under different circumstances.
Use Family Roles to Your Advantage
One school of thought I have only recently discovered is around family dynamics and how roles play into them—the rebel, the jokester, the serious one, the responsible one etc., etc. One of the things that's so interesting about this idea is that people can switch roles depending on who they are with. A person might be known as the serious one in their own family, but they could be the jokester in their friend group. That might be because they want a chance to stretch their personality legs, or it could be because the friend group already has a person taking up the serious role. People are multifaceted. The fun thing about side characters (mainly when writing in third or first person rather than omniscient) is that you get to place them in a role and (if you are so inclined) leave them there. Your main character might never discover their other side. But if your protagonist is getting a bit stale, try to surround him/ her/ them with a different setting or group. If your character's main personality trait is that she is brave, then confront them with someone even braver, shake her out of her role, and give her a bit of competition. This is where being a panster is convenient. You can throw a scene at your character and challenge them to be more interesting. If you are a plotter, you might want to plot this arc. It will likely be smoother and more engaging for your dastardly plotting.
Know Your Crutch Character Mannerisms
One excellent piece of advice I got was to find my crutch words and phrases. While I was writing or editing, I kept a list (that I kept losing) of all the terms and words I found myself reaching for. Three biggies for me were: really, for a moment, and a little bit. I have many more. I didn't try and avoid them while I wrote. Instead, I did a search and replace once the book was finished- still a difficult thing to do; I love those phrases; that's why I use them so much!
Find your crutch character fallback. Mine is moaning. Whenever I didn't know what to do with my character, she would fall back to moaning. Not a desirable character trait. To keep a scene moving, I might let her moan, but then I would go back and rewrite it. Unlike crutch words, I didn't wait to the end, and for a good reason. My moaning, whinging pain in the ass protagonist was building a personality while I wrote her. And I find that if I let her have her way and moan to her heart's content, it would be part of the character make-up by the next scene. I needed to fix it before the trait became too ingrained. You might work differently, but I think it's a good idea to know your default. That way, any characteristics are intentional rather than accidental.