We all have quirks.
One of mine is that I love traditions. So every July 4th week, I know I'll be dragging my kids to a blueberry farm at least once so we fill our fridge and hopefully our freezer with fresh blueberries. This year we went twice in three days -- so far. But my breakfast of choice is homemade oatmeal with blueberries on top. Every day. Of the year. Over and over. Quirk.
In my novel Stars in the Night, the heroine Audra has a charm bracelet that she plays with when nervous. In A Promise Forged, the heroine Kat is a ballplayer with the inaugural All American Girls Professional Baseball League in 1942, so she borrow a quirk from my grandpa and is constantly running a baseball through her fingers.
In real life, I have a friend who always has a long-sleeved sweater on, no matter that it's 90+ degrees outside. I have another friend who keeps a running to-do list on a clipboard with sheets of notes -- in what appears to be random order. But she's one of the most organized people I know -- even if I could never make her system work.
Think about the people you know...most of them will have some unique quirk. Does she pluck their eyebrows out compulsively? Does she always wear big necklaces in layers? Does he always have a Swiss Army knife that he has to mail back every time he hits an airport?
These are the details that make people unique. They also serve as tells. "She must be nervous because she's doing X..." Your characters need these, too.
So what's the best quirk you've read in a character or given a character? And what's the best quirk you've seen in real life? I can't wait to see your answers!