Marked in the placement of the hinges. Last year I bought 4 sets of hinges when Brusso was doing their sale on the small size hinges they offer. I'm glad I finally had an excuse to use a set!

I figured out the placement by following instructions from "The Joiner and Cabinet Maker" from the Lost Art Press. The center to center spacing of the hinges is equal to half the width of the total box. I then simply centered them in that spacing. I marked the locations out with a pencil, then used a marking knife with the physical hinges to cut in the locations of the mortise.