OS X El Capitan: Use the Keyboard Viewer
Click the Input menu in the menu bar, then choose the input source for the language whose keyboard you want to view.
Choose Show Keyboard Viewer from the Input menu.
If the command isn’t shown, choose Apple menu > System Preferences, click Keyboard, click Keyboard, then select “Show Keyboard, Emoji, & Symbol Viewers in menu bar.”
Press the key on your keyboard that corresponds to the character shown in the Keyboard Viewer, or click keys in the Keyboard Viewer.
Press a modifier key, or a combination of modifier keys, to see special characters or symbols you can type. For example, hold down the Option key or the Option and Shift keys.
If you changed your input source or keyboard layout in step 1, be sure to change it back, if necessary.
If you don’t see a specific character or symbol, try using the Character Viewer.