How does one add keyboard languages and switch between them in Linux Mint 16?

I've added languages in Language Support but I do not see the language icon in the panel tray, nor can I switch between languages.

This assumes you have other languages already added in Language Support. (To check this, Menu > Language Support)

Now to make the keyboard language appear in the Panel:

• Menu > Keyboard > Layouts > Add (+)

The icon 'en' or your language should now appear in the right panel tray. Click it to switch language.

In previous Mint versions, the shortcut for switching language was LEFT SHIFT + CAPS.

It seems now there is no default, and it must be added:

• System settings > Keyboard > Layouts > Options > Switching to another layout

Keyboard Preferences is also accessible by right-clicking the language icon in the Panel.

For Linux Mint 18 Cinnamon

Menu > Keyboard Preferences > Layouts > Options > Switching to another layout.

Mint 18.2 (Cinnamon)
Menu > Keyboard Preferences > Layouts > Options > Switching to another layout:

Go to menu , search for Regional Settings. Switch to Keyboard layouts tab. Click Options button. Search for Key(s) to change layout. There isn't a default one so you have to tick the combination you like. Enjoy.