How did the Chinese manage to get Acupuncture right?

I grew up in a Daoist family, and I'm very familiar with a lot of the Chinese energetic practices (such as healing). This is mostly due to me knowing a master personally.

When I was in highschool, I went on a trip as part of a medical internship thing to visit a TCM hospital (where the students were one of the first batches of americans to be exposed to the stuff). When we got there we were given a lecture on how accupuncture was created. It went something like the following;
"There were lots of wars in China, and people would get hit by arrows a lot. Over time, people would notice after getting hit by arrows (assuming they survived), health problems they had such as toothaches would go away. Overtime, these incidents were developed into the system of accupuncture we have now."
I raised my hand and said "um, that's bulls**t." Since then I've come to notice this explanation is still the prevailing mindset in the west.

Anyone that progresses with Daoist Meditation or an energy practice such as Tai Chi will eventually hit the the point where they can feel the energy channels in their body. Some of the masters mapped out one of the energy systems they found (the meridian lines), and then was used that to develop accupuncture, which was subsequently taught to people who did not have the same level of ability as the masters, but nonetheless were able to get health results.
The practical consequence of this is that the meridian lines are positioned slightly differenty on each person. As a result, if you see a good accupuncturist that can feel them, they are able to get the needles in exactly the correct place (and hence allow for a much better treatment), while someone with less sensitivity just has to go off the charts they learned.

I wondered for a long time reason why people would take the arrow explanation for being truth, since it's so absurd, but I think I've figured it out.
Modern medicine still doesn't really awknowledge accupuncture works. They've grudging admitted that it does something since there's plenty evidence to show it does, but a lot of anecdotal explanations are offered which ignore the actually energetic theory being true. In this same vein of thought, since accupuncture is an enigma "that just happens to work," it makes much more sense to regard it as something that was the product of coincidences rather than people applying the contested theories accupuncture is based on (say that people have Chi/Qi).

I hope that answers your question. I tried to be really thorough!

One day, a man called Ho Yin Cheng got a whole load of needles and thought it would be funny to throw them at someone. When they were all stuck in the person's back, but they had shown no indication that they knew the needles were there, he asked them "I just stuck a load of needles in your back, does it not hurt?"
They replied "No. Go away."
Then Ho Yin exclaimed "I have discovered acupuncture!"
The end.

Thru trial and error..until they got it right..

Several thousands of years of using it I would guess. What other 'modern' medical technique or treatment can make that claim?

Practice, practice, practice.
And Thanx Alex.