This Haagen Klaus paints a rather grim picture. He says the Incas didn't consider children to be human beings, got no special treatment and their throats were just slit, and voila: job well done.
The next paints a bit different picture:
Capacocha was the Inca practice of human sacrifice, mainly using children. The Incas performed child sacrifices during or after important events, such as the death of the Sapa Inca (emperor) or during a famine. Children were selected as sacrificial victims as they were considered to be the purest of beings. These children were also physically perfect and healthy, because they were the best the people could present to their gods. The victims may be as young as 6 and as old as 15.
Months or even years before the sacrifice pilgrimage, the children were fattened up. Their diets were those of the elite, consisting of maize and animal proteins. They were dressed in fine clothing and jewelry and escorted to Cuzco to meet the emperor where a feast was held in their honor. More than 100 precious ornaments were found to be buried with these children in the burial site.
The Incan high priests took the victims to high mountaintops for sacrifice. As the journey was extremely long and arduous, especially so for the younger victims, coca leaves were fed to them to aid them in their breathing so as to allow them to reach the burial site alive. Upon reaching the burial site, the children were given an intoxicating drink to minimize pain, fear, and resistance, then killed them either by strangulation, a blow to their head or by leaving them to lose consciousness in the extreme cold and die of exposure.
Early colonial Spanish missionaries wrote about this practice but only recently have archaeologists such as Johan Reinhard begun to find the bodies of these victims on Andean mountaintops, naturally mummified due to the freezing temperatures and dry windy mountain air.
http://en.wikipedia....wiki/Capa_cocha
Btw, the descendents of the Incas nowadays use llama fetuses instead, and a place where you can see these fetuses being sold for that purpose is the Calle de Brujas or Witches' Street (or something similar) in La Paz, Bolivia. And it's best not to take a picture of anyone in that street (and certainly not of children - they think you are stealing their souls) for they will hunt you down and slap you with the intestines of a freshly killed llama, lol. Well, that was in 1991, anyway.