With the launch of OS X 10.9 'Mavericks', Apple introduced a new way of language preference settings, which has also been adopted in 10.10 'Yosemite'. It now looks like this:
By default, Apple provides only the language you selected at the first startup after installation and U.S. English. If you have would like to restore the 'old' way of a long list of languages, here're the resources you'll need.
The screenshots above are from a fresh-installed last-updated version of OS X 10.8 'Mountain Lion', which I just captured from a virtual machine. I selected English as the system language and left everything else by default, and thus the order above should be the official default order.
After manually adding and changing order of new languages in your own OS X, it should look like this:
P.S. Just in case - you don't need to restart after making each change in language settings. Click on 'Not Now' and continue your work.