Sounds like it's been lots of fun in Yale's research labs lately: they've been busy finding the science-approved best way to throw things.
The answer? Slowly.
Reporting in the Royal Society Open Science journal, M. Venkadesan of Yale and L. Mahadevan of Harvard found that the most accurate throws were underarm, and s-l-o-w. But if you need to throw faster, you need a different tactic:
"At higher speeds, the shallow overarm throw is most accurate, particularly for targets at or below the arm pivot (equivalent to the shoulder).
[...] The physics of projectile flight dictates that throwing slowly generally maximises accuracy, and if it becomes necessary to throw fast, an overarm style is the more accurate one."
Apparently, faster launches are less accurate because there's more potential to get the angle wrong, and that error is then amplified by the speed. In a slower or more curved throw, you have more room to make mistakes.
There's also lots of useful info about how to be a better darts player:
"The optimal dart throwing strategy is an overarm throw with an optimal release angle of 17–37° before the arm becomes vertical, and a corresponding optimal speed of 5.1–5.5 m/s. At this speed and release angle, the dart would be released 44–35 ms before the hand reaches the zenith.
The best overarm throw is 7–20% more accurate than the best underarm throw, as found from the ratio of the accuracies. The overarm throwing strategy with a larger radius of curvature (0.8 m) and higher speed (5.5 m/s) is the most accurate of all, consistent with observations."
Try repeating that one at the pub.
The report goes on to say that humans, who learnt to throw spears while hunting, are unusually good at throwing compared to the rest of the animal kingdom. To quote the BBC, "monkeys also throw things, but they are really bad at it."
Probably for the best. [BBC]