Here are a few simple guidelines for making character quirks:
- Try to make quirks that are both fun and memorable. You want the reader to enjoy the quirks and you want it to be fun for you, too. Also, quirks are better when they are memorable. There is a certain sense of joy and even anticipation that readers can get when that quirk applies.
- Consider how often your quirks might affect that character. You could make quirks like a stutter that only affect speech, or you could make quirks like a fear of water. Both of these quirks will happen quite often and might get in the way of the story progressing. On the other hand, you can create quirks that only happen every so often. A good example of this is from the anime Ranma 1/2 where he had a fear of cats. It didn't apply to every episode, but it would come up every now and then and made him more interesting.
- Consider if your character will get over his quirks or not. This can be huge. Perhaps a character has a thing where when she's nervous, she plays with her hair a lot and another character points it out to her. Is it someone she likes? Is it a friend? Is it her family? And more importantly, what is she gonna do when she realizes she does this? Will she try and get over it, will she embrace it? Who knows? It's up to you to decide.
- Pick quirks that will make your character unique. A dwarf with a drinking problem isn't really too creative. If something happens when he's drunk, however, well... that could get more interesting. Quirks are what sets your character apart. Make sure to be creative.
- Don't be TOO creative. As opposed to number 4, if you get too creative, it might get absurd. If you're a good writer, you might be able to make it work, but if you get too intricate and too creative with your character quirks, you might end up with a lot of problems later down the road.
- Your character quirks are not the story! I mean, you could write a story about a guy who gets over his bed-wetting problem, but quirks are mainly intended to supplement an already interesting plot. So don't focus too much time on them. If you're writing a novel, you don't want half the book to be about his quirk and how much trouble it gives him. Try and limit yourself to how often the quirk comes up or readers will get bored of it. If it's a short story, I'd actually say you can put more focus on it because it's shorter readers are less likely to grow bored of your characters strange quirks. However, try to be mindful of how much time you spend on quirks.
- Lastly, not every character needs interesting quirks. Some characters can just be normal people, or vampires, or whatever you're writing about. However, I think for a novel-length book, I'd suggest having at least 4 or 5 characters with minor quirks, and perhaps even 1 or 2 with some major quirks.