Preview open windows from the Dock
Rest the pointer on a Dock icon and DockDoor shows a live thumbnail of each of its windows.
Tips tagged #dock
Closing a window does not quit the app
The red dot leaves the app running. Command-Q is what actually closes it, and the Dock tells you which is which.
Set up the Dock the way you want it
Hide it when you are not using it, keep only the apps you open, and stop minimised windows piling up on the right.