I have seen pictures of personal ranges that have a series of impact berms set up so that shots for each progressively longer range pass beside shorter range berms. Having an impact berm right behind a target helps reduce the chance of shots impacting short of the target and ricocheting over the berm. In general terms, it is better to shoot north, and I would take the dominant wind direction into account when laying out impact berms, so that shorter range berms are down wind of longer range berms.