A picture might paint a thousand words, but I feel like a gesture is just as eloquent. Here's a list of my top five gestures or habits that I've included in writing... the list implies an order, but I like all of them equally.
Five: Curling hair
[Redacted] seems to be thinking the same thing, because she shuffles her feet awkwardly and curls her hand around the length of her hair, pulling it away from the nape of her neck.
Characters playing with their hair can be read in a bunch of different ways. To be honest, this mostly occurs as a thoughtful gesture in my writing, rather than playful or sexual - characters don't tend to fluff their hair in my work. But they do rub their heads if they have short hair, especially if they're stressed... which is something I do too, haha.
Four: Shifting from foot-to-foot
[Redacted] watches as the human shifts from foot-to-foot, tucks his arms about himself more closely, then smiles tensely.
This is almost always an indicator of discomfort for characters. In the fandom that I write in, one character does this 'canonically' (which means it's written into the actual source material), and he's a character who is in fairly constant physical and psychic distress. Since I noticed this about this one character, I've included it for others as well (as you can see in the example for five) - not as often, but that gesture is so indicative of wanting to run away, to get physically away from something that you find uncomfortable, that it's very evocative to me.
Three: Sniffing
“Vastly over-rated, that,” [Redacted] sniffs, and drags on his cigarette again.
A sniff of distain; a constant, low-grade cold; a thoughtful sniff accompanied by a shrug, as if the thought simultaneously matters and doesn't. A small, sharp inhale can also indicate suprise. Sniffing, I think, is vastly underrated as a gesture; honestly, I think most people are so unconscious of doing it that they don't even consider it a gesture. But if you've ever sat next to a sniffing person on public transport, or noticed that little inhale, you probably know it can be pretty grating under particular circumstances - more annoying for listener than performer. It's that, coupled with the gestures potential nonchalance, that makes it interesting to me.
Two: Nail biting or chewing
[Redacted] purses her lips and looks down at the table. She almost seems to shrink into the seat, raising a hand to her mouth and chewing for a moment on the thumbnail. “Did he say anything to you?”
Another thing that I do myself - I have a tendancy to chew on my thumbnail, but I have written characters who will tear their nails or bite them very badly, which is a habit I used to have. Another indication of stress, I suppose... but the chewing is also used as a function of thinking. It's interesting to me how much our brains need our bodies to be doing something in order to think, even if it is just a repetative tapping or doodling... or, in this case, chewing.
One: Interlacing fingers
He swallows, then interlaces his fingers, bowing his head. “I feel…” he begins, then stops. Never has he felt so old, so vulnerable.
It tends to be high-class characters that do this in my work. I regard this gesture as being a bit patronising, almost school-ma'am-ish... but also very defensive. The interlacing of fingers is often accompanied by a tilt of the head, so it can be questioning as well.
This is the magic of gestures, I suppose - they can be read in multiple ways, just like any form of communication, and it's not always possible to sort out intended meaning from recieved meaning, especially when you put all the cultural coding that we as humans seem to be fascinated with into the mix.