I would use galvanized ring shanked box type nails. I would put two in each shingle. I would not put them too close to the edge as they will crack. Probably about two inches in. I would consider the stagger method, it does look good.
Corners, I would just cut the shingle as close to the angles that are needed. It is not imperative to be exact.
When up, I would strongly consider sealing the shingles.