<p>I've managed to mostly ignore all this multi-byte character stuff, but now I need to do some UI work and I know my ignorance in this area is going to catch up with me! Can anyone explain in a few paragraphs or less just what I need to know so that I can localize my applications? What types should I be using (I use both .Net and C/C++, and I need this answer for both Unix and Windows).</p>

Check out Joel Spolsky's
The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!)
EDIT 20140523
: Also, watch
Characters, Symbols and the Unicode Miracle
by Tom Scott on YouTube - it's just under ten minutes, and a wonderful explanation of the brilliant 'hack' that is UTF-8