I prefer disassembling the cake and cutting in rectangular slices that measure 1 X 2 X 4 inches.  I think the slices are easier to control and look neater on a plate.

Still, some people prefer the wedge style cutting.  That style has fewer servings and is a little more complicated.  Here is a diagram and instructions for cutting.  Usually when figuring price per serving, the wedding slice (1x2x4) measurement is used. The 4 in the measurement is the height of a typical two-layer cake.