When cutting across the grain on the edge of a board or across the face of a narrow board, always cut halfway in from each edge first, removing the center part last. By the same token, when trimming end grain, always work from each edge in toward the center.
Allowing a chisel to run off the end will almost certainly result in splintering or chipping the corners.
To cut recesses, such as those which may be required when setting hinge leaves into the edge of a door, always use the chisel vertically first. Make shallow cuts (tap with a mallet for this) at each end of the recessed pocket. Then, make additional cuts across the grain at several points along the length of this recess so that when the wood is chipped out afterward individual chips will be short and less likely to split across into other parts of the work.
After these crosscuts have been made, the wood is removed by chiseling across the grain with the chisel held with the beveled side down.
After most of the wood has been removed, the chisel is turned over (bevel side up) for final paring cuts which will shave the recess to the exact depth required.