Use Cmd-w to close windows and Cmd-q to quit applications. Also, when Cmd-Tab'ing, you can hold down Cmd and hit q to quit an application. It's a quick method

Use Cmd-w to close windows and Cmd-q to quit applications. Also, when Cmd-Tab'ing, you can hold down Cmd and hit q to quit an application. It's a quick method for closing a lot of applications.