1.move between windows via 'CTRL-W w', or CTRL-W arrow key, or
CTRL-W h/j/k/l for left/up/down/right;
2.close a window via 'CTRL-W c' (or good old ':q');
3.make the current window the only one via 'CTRL-W o';
4.split a window into two via 'CTRL-W s', or 'CTRL-W v' for a vertical split;
5.open a file in a new window via ':spl[it] filename'.