Window commands that I use all the time:
<C-w> o- closes all other windows besides the current one.
<C-w> ^- go to the "alternate file". Very useful for swapping between 2 most recent files.
<C-w> T- if you have a window open in a split and you want to move it to a new tab, focus the window and execute this mapping.
<C-w> [h,j,k,l]to just
<C-[h,j,k,l>for much easier buffer navigation.