I was inspired to create this post after Incarnadine's post about spin pins. I'm able to quickly pull my almost-hip length hair into a neat, secure bun that doesn't come out with vigorous exercise, using only one hair stick.
Your hair doesn't have to be straight, although it's much easier to learn by watching me put up my straight hairs since you can see where the loops go. I tried the same on Lauren's (jazz_lover) curly hair and it worked fine too.

Style 1:
Style 2:
These are slightly messier than the intended result because I was taking pictures by myself with a self-timer when I was doing it.
To begin: you need to comb your hair out. I was able to put hair up when it's freshly washed without any styling products, but I think it holds a little better with day-old dirtier hair.
Style 1:
Hold your hair in a ponytail. It can be high or low. I like mine to sit around the middle.
Twist clockwise, and start to wrap your hair around your thumb.
Then hold your left hand there, with your thumb pressed against your head for support.
Take your right hand and start wrapping the tail of your hair counterclockwise against the base of the ponytail, between your thumb and your head.
Wrap until almost all of your hair is looped.
Take the hair stick, and put it in the loop of hair that your thumb was in, in the same direction your thumb points.
Catch the loop of hair underneath (that contains the majority of your hair wrapped around the ponytail base) and push.
The loop originally created by your thumb should expand slightly, and push the hair stick out, so it sits above the loop.
Here's a video of the whole process...excuse my silly face
Style 2: start off with combed hair with small amounts of styling product if you desire. Gather your hair into a ponytail wherever you want the bun to sit.
This time, hold your ponytail with your left hand, and thumb beneath the ponytail.
Wrap your hair counterclockwise around the base of the ponytail, so the loop forms between your thumb and your head.
Wrap, wrap, wrap, until all your hair is in that second loop.
Put the hair stick into the loop made by your thumb in the same direction as your thumb is pointing.
Catch the right side of the larger loop that you made by wrapping the rest of your hair around the ponytail base.
Push your hair stick out of the center of the larger loop. And there you go, another neat and pretty bun! Here's a video if you're still confused.
I hope it helps! You can find hair sticks in many online boutiques, or if you have any Asian stores in your area. I used a small Hello Kitty chopstick because it contrasts the most with my dark hair, but I usually use a black one so it doesn't stick out, or a blinged out metal one if I'm wearing it to a formal event.
~Haili