Tiling window managers with keyboard shortcuts for super quick window and virtual desktop switching as well as full screening focused windows. Obviously, more screen is always better, but I don't feel I loose a lot of efficiency when I'm unplugged and out and about, with my 14 inch notebook screen.

Apps that cover the screen, shortcuts to switch between them quickly, and generous use of spaces.

I used to think this but I realized I needed glasses. :) Still I couldn't use 13 inch screens all day.

and laptop keyboards.