There are two locations where you can define the button’s location: dconf and gconf.

The dconf-method works for most of Gnome Shell and Unity. However, e.g. Chrome is using the “old” gconf-setting.

dconf

Install and run dconf-editor.

Go to org → gnome → desktop → wm → preferences and find the setting button-layout. The default value is: appmenu:close. To just add the minimise/maximise buttons (e.g. in Gnome Shell), change it to: appmenu:minimize,maximize,close.

To just move the close button to the left, use: close,appmenu:. (The : separates the buttons on the left and those on the right.)

You can also mix it up, e.g. close,appmenu:minimize,maximize.

gconf

Install and run gconf-editor.

Go to apps → metacity → general and find button_layout. Here, the default value is :minimize,maximize,close.

To get everything to the left, use close,minimize,maximize:.