How to get your Mac to write in another langage - in this case, Russian

In the International System Preference Pane, click on Input Menu, at the bottom check show input menu in menu bar. This let's you quickly move from Russian or any other keyboard to English. Also, on Select the keyboard layouts, input methods, and palettes select Character Palette and Keyboard Viewer. Then make sure Russian keyboard is also selected.

Now, on the menu bar under the little flag, select Russian.The keyboard now changes to a Russian keyboard. In the flag menu bar, make sure to Show Keyboard. Now you will see how keys are mapped into Russian. You can type the keys to see which one corresponds to the new mapping. It would be interesting for Apple to design a keyboard whose labels change with the setting of the language.