When you receive acupuncture, the acupuncturist will usually do an assessment of your pulses in your wrist, and look at your tongue. Along with your complaints of symptoms, the acupuncturist will be able to identify meridians (energy pathways that travel throughout your entire body and go through different organs) that may be congested. The idea is that our bodies have a vital energy (chi, qi, or prana) that flows through our bodies. When there is congestion in these meridians, we will feel symptoms, pain, decrease energy, etc. By placing needles along the meridians, it provides an escape for the congested energy and lets the chi flow freely, the way it was meant to. During different phases of our healing and with different symptoms, the needles will be placed in different places to optimize the flow of chi. Its definetly not random as to where they place the needles, its just a very intricate system that most people don't understand. Thats why most acupuncturist will have a chart on the wall of the body and all the meridians that go through our body (kind of like veins and arteries). The needles are very fine, like size of hair and should not hurt when they are placed.