Personally I'm very fond of three screens, it lets me split information by level of attention required: the center one is for what I'm focused on, left screen i

Personally I'm very fond of three screens, it lets me split information by level of attention required: the center one is for what I'm focused on, left screen is additional information I might need (like documentation or console output), right screen for things I don't really need to pay attention to (given my peripheral vision isn't as strong on the right). The positions are set in such a way that I can glance at the left without turning my head, whereas the right side requires me to switch focus / turn my head to give it my full attention.