Stroke is to a dart player what pitching motion is to a baseball player. The difference is the dart player is trying to throw his pitch in the middle of the strike zone at a consistent speed. A major league pitcher would have little success with this method outside of the batting practice, so perhaps a comparison to a golf swing would be a better analogy.
Anyway, for the sake of consistency, a dart should be thrown at the same speed with the same motion - which is akin to the beauty contestant who wants world peace. It sounds nice, but it is much easier wished for than had. Most of the very good dart throwers I have ever seen employ a sharp stroke of the forearm. The wrist is cocked backward and most of the motion in the throw comes from the forearm and the wrist. It's like the crack of a whip, with the dart being at the tip. Make no mistake; this is one of the hardest parts of the equation that yields accuracy.
In my practice sessions I am ever trying to achieve consistency in my stroke. This is easier to do when all three darts are thrown one right after another; it's often referred to as rhythm shooting. And indeed many dart players seem to throw their darts in groups of three, rather than one dart at a time. That's fine when you're in a groove, but it can be troublesome when your darts are erratic.
A couple of personal observations here. A faster dart stroke is easier for me to repeat than a slow one. Most good players I have seen throw a fairly hard dart, and they all seem to employ a snap of the wrist at the end of the stroke. Paradoxically, I throw my best darts a little off speed. When I am shooting well, my stroke is at that perfect speed, which is just a tad slower than normal. But when I fall into a slump, it is usually because my stroke is too slow. This comes from trying to aim the dart too much instead of trying to throw it. The message here is to cultivate the highest combination of dart speed and accuracy you can attain.
The end of the stroke is most important. I like to finish with my hand extended at eye level and the target centered between my thumb and forefinger. You will see a lot of players with an exaggerated wrist snap and no follow through. They short stroke and they seldom hit much. If I take my follow through too far, I lose sight of what I am throwing at and usually my dart hits low. I try to keep my dart hand up around eye level on follow-through.
I have also done a lot of inconclusive experimenting with where to anchor the dart just before the throw. Under the eye, in front of the chin or cheek would seem to be the right spot. However, what works best for me is to hold the dart above the eye and off to one side. Here my hand does not obscure what I am shooting at, and my dart still flies on a good line to the target. But most of the pros I have seen anchor somewhere in front of the chin, and below the line of sight.
The best way to cultivate stance, grip and stroke is through lots of practice. Fortunately, darts is a game well suited to individual practice. You don't need a partner, and you can coach yourself if you know what to look for.
Until Next Time!