This is probably my favourite method of working in the round. I like that there is only one needle, so if I've been working on a garment I've already got the correct needle to hand. I find that I can pick up a bit of speed with it with a flexible cord that's long enough I don't get any ladders.
You need to have a circular needle that is at least 32"/80 cm in length with a flexible cord. If the cord is stiff it will create ladders at each side.
The video is the best way to learn this technique but here's a basic overview:
That's all there is to it! It takes a few rounds before it joins properly but it's really handy not to have to get another whole set of needles to work smaller circumferences.
Some knitters really dislike the cord loops on each end and find that they get in the way. If this is you you might move on and take a look at some of the other circular techniques.