So a lot of things I've read about writing have emphasized giving characters flaws and strengths to make them more realistic, but my favourite thing to do is to give my characters "quirks" that are pretty much neutral. I find that these tiny details really bring them to life. The kind of quirks I'm talking about are the subtle things that people really only notice about themselves or close family/friends they've observed for years.
These quirks can be behaviour patterns, subtle personality traits, preferences, anything, really. A couple of examples: My sister tends to take three trips in and out the front door before she actually leaves the house because she usually forgets something. I'm a fairly clumsy person, but because I've had so much practice at tripping and dropping things, I'm now quite good at recovering my balance and catching things before they hit the ground. One of my friends tears up whenever she sees something really cute.
Any quirks that people would like to share (either your own or things you've observed) and wouldn't mind being used in a work of fiction? I'd particularly like a list of idiosyncratic things that males do because males are somewhat of a mystery to me. Not only are long lists of anonymized quirks allowed, they would be greatly appreciated.