I just completed a workshop where we built a 14x20, three cant, two story (mini) barn. We used "square rule" layout and learned to do all the work with human-powered tools. 1//16" is a mile if it's in the wrong place.
Learning to be dead accurate with layout and then SPLITTING the lines was key to making the puzzle fit together.
It ain't easy but it's hugely satisfying to learn how to build a beautiful and functional building with simple tools-a square, pencil, chisel, saw, mallet, and manual/mechanical drill. Square Rule layout eliminates errors from unplaned, not-so-square lumber.
Sarah K. Highland was our instructor. I'm going to do a few very small projects before I tackle another building.
Ms. Highland is a member of the TF Guild, they have a site. And there's a forum. She recommends: Timber Frame Construction: All About Post and Beam Building - Jack A. Sobon as representative of the techniques she uses and teaches. I just ordered mine.