Use your viewpoint

Imagine standing at A and facing B. The arrow from A to B sets your front. You stay at A; only the direction you face changes. The map keeps north at the top.

Here B is east of A, so you face east. Your right side points south, where C is. C is therefore on your right. The solid arrow shows your facing direction, the dashed arrow points to C, and the 90° arc shows a quarter-turn to your right.

Now stand at A and face B to the northeast. Keep looking along that diagonal. C is southeast of A.

Turn a quarter-turn clockwise from your facing arrow to the dashed arrow toward C. That puts C directly on your right. The same method works when your front points diagonally across the map.

In this new map, stand at A and face B to the southwest. Keep your position at A. Find C to the southeast.

Choose the side of your body that points toward C. Use the facing arrow to decide your own left and right.