The Purl Stitch
The Purl stitch is the same resulting stitch as the knit stitch, if you were to look at the knit stitch on the reverse side.
Which style to learn?
The below styles all create the same resulting fabric, and are interchangeable. Experiment and see which you enjoy most! The throw/English method is easier to execute and learn at first, great for teaching kids, or for those who want a guaranteed-success approach. That said, some people who start out with English method find themselves later switching to Continental, a compelling trend. The "best" method is simply the one you feel most easy with, the method you most enjoy.
Continental Method
Also known as the German Method
And here is a short close-up shot: view video
Yarn is held in left hand. The middlefinger (or, more commonly, the index finger) is used to push the yarn down and to the right, to where the right needle can easily push it back through the stitch. This method requires fewer hand movements than the English method, offering a speed and fluidity which many knitters are attracted to. It is quite a feat of agility to execute this method at first, but if one's hands take to it, it can be quite smooth and enjoyable. This is the method I use, and demonstrate in the Continental purl videos on this site. Videos where the yarn is held in the left hand like this, all have a pink icon.
This method of purling, when combined with Continental Knitting, makes for a very fast ribbing. Here's a fast-paced demonstration of Knit 1, Purl 1 ribbing worked with these methods: view video
Elizabeth Zimmerman employed this method (as demonstrated by a knitter on YouTube). Really, the point is to fetch that yarn through that loop, from front to back. Do whatever works for you! Just be aware that if you go around the yarn the "easy" way, you are then purling using the Combined method (see below).

English Method
Also known as the Throw Method or the American Method
And here is a short close-up shot: view video
This is the most common purling method in the US. Easy to execute! Children can purl this way. No nonsense, you will be able to form a purl stitch with ease, and follow pattern instructions without modifying. Yarn is held in right hand, then, by necessity, brought to the front of the work if following a knit stitch, and, wrapped around the right needle before pulling the stitch through. Videos where I hold the yarn in the right hand all have a blue video icon.

Combined Purling Method
This method produces a true purl stitch, but there is one important distinction: because the yarn is wrapped around the needle clockwise instead of the more common counter clockwise, the resulting stitch is oriented differently on the needle, and must then be worked accordingly on the following round.
Because the yarn is held in the left hand, it has the speed advantage of Continental purling, and it is easier to manipulate than Continental.
One must be aware, however, that directions on standard patterns need to be adapted to accommodate the different stitch orientation. Decreases and increases, and other stitch directions, need to be done differently than described in a pattern, or the stitches need to be re-oriented before executing them. l believe that wrapping the knit stitch the other way around, to create a similarly oriented stitch, is employed at times, to create a desired stitch orientation.
Here's a site that has more info on knitting in the Combination way.

Norwegian Purling Method
No one at my 3 local yarn shops had ever heard of this method. I came across a description online, and after much confusion, and the help of the brilliant Linda Daniels at Northampton Wools, we finally got it! A Norwegian friend has confirmed, "Yes, this is how the purl stitch is done!"
What's mind blowing about this method is that it's a purl stitch worked with the yarn in back of the needle. (!) Apparently, this is the most common method used in Norway, Denmark and Switzerland.
The trick to doing this right is to bring the right needle behind the working yarn before diving down into the stitch, or you end up with a YO between stitches.

Knitting Back
view continental video view english video
Not a simple substitute for all purling needs, but handy in some circumstances.
This produces the same exact stitch as the purl stitch, it just does it with the knit side still facing you. This is a great method if you are working a narrow piece of knitting, as when doing Entrelac, and are tired of having to turn the work every five stitches. With this method you can work a whole entrelac piece without turning the work!
The limitation of this stitch is that you can't easily alternate it in the row with knitting, to knit ribbing for example, unless you are creative and motivated enough to figure out "purling back" as well.
This may look like "Left Handed Knitting," but you wrap the yarn the other way for that method.
