What tactics were used, what tribes faught and over what? Where any tribes completley wiped out. How did the introduction of horses effect how they conducted war?
What region and time period are you interested in? The Inca military of 1495 was drastically different than a Maya city's warriors of 595 AD and the Lakota at the 1876 Battle of Litte Bighron.
A pretty decent discussion of wars in the Northwest Coast area can be found here. You mention intertribal warfare. Wars in the northwest were never tribe against tribe. It was not possible to rally an entire tribe. The vast majority of conflicts, at least in the northwest, were village against village.
Rather than re-type a lot of information I've discussed elsewhere, I'll just point you to the rabbit hole and send you tumbling into an Iroquoian Warfare Wonderland. The post linked to discusses the war between the Haudenosaunee (the Iroquois Confederacy) and the Erie confederacy in the 1650s. The follow-up post there contains links to additional posts concerning tactics and equipment (with siege tactics being mentioned in yet another link), Iroquoian politics with a bit about how it influences war, and the fate of war captives. There's some bonus material sprinkled through out on other peoples like the Chickasaw and early colonial Mississippians. Enjoy, and if you have any follow up questions feel free to ask them here rather than scattered around in those old posts.