CTRL-b, "
- Split window horizontally (i.e. split and add a pane below).
CTRL-b, %
- Split window vertically (i.e. split and add a pane to the right).
CTRL-b, UpArrow
- Move to the pane above (I prefer to rebind this to CTRL-b, k to be similar to Vim).
CTRL-b, DownArrow
- Move to the pane below (I prefer to rebind this to CTRL-b, j to be similar to Vim).