This simple, yet immensely effective tool traces its origins back to Scandinavia; "nøste" - ball of yarn, "pinde" - little stick, literally translated means “a little stick for winding balls of yarn.” I find the nostepinde indispensable when I do my drop-spindling as they are portable and provide a gentle way to ball yarn without over-stretching.
To Begin: Hold the tail end of the yarn against the handle, and wrap the yarn around the top groove of the nostepinde a few times, to hold the yarn in place. You may alternately tie a loose half-hitch knot to secure the tail of the yarn.
Wrapping the "Core": Hold the handle of the nostepinde in your non-dominant hand (Note: this will be the left hand for most; lefthanders please reverse any right/left references). Starting around the center of the smooth tapered section, begin winding the yarn so it slightly overlaps itself.
Make sure you think about the tension you are using -- the yarn should be tight enough not to slip around on the nøsty, but not stretched. Overstretching can damage most yarns, eliminating their elasticity, especially when stored for periods of time.
To continue with the ball, start wrapping in a diagonal pattern, bringing the yarn from the lower right-hand "corner" of your core wraps, up across the core to the upper left-hand "corner". Be patient, as the yarn may fight this process somewhat. I find it most useful to hold the nøstepinde at a 45° angle in front of me, winding straight away from and toward my body.
Turn the nøstepinde slightly in your hand after each wrap so that each diagonal lies down next to the one before. Keep winding diagonally while slowly turning the nøstepinde away from you. With practice, your winding hand will fly ‘round and ‘round, your other hand intuitively turning at just the right speed to lay the wraps down neatly.
Shaping the Ball: If you place each diagonal wrap right up against the side of the nøstepinde as you proceed, the height of your ball will increase along with its diameter. It will end up looking rather like an egg. There's nothing wrong with egg-shaped balls of yarn -- they work fine...
...but it’s equally easy to create a ball with a flat top and bottom, which stacks most prettily on the shelf. While you're winding diagonally, visualize where the top left and bottom right "corners" of the ball are going to be. Place your wraps out at these "corners," and do not continue to increase the height of the ball.
When your ball is done, or you run out of yarn, untie the knot at the groove, (if you tied one), and slide the ball off the top.
With practice, you'll soon be able to wind at light speed!
Enjoy your nøstepinde!