The simple rule is, always read and write using the same encoding, and
be aware when something is converting between characters and bytes
behind the scenes - servlets for example.  Make sure the font you're
viewing the result in contains the glyphs for the characters you're
trying to view (helpfully the no-glyh character is often the same box
or question mark used to mean no-mapping in the encoding...requiring a
hex editor to check the underlying bytes), and be certain the viewer
is showing the result in the right encoding (the cmd window here, or
say the Eclipse output window is another notorious spot)

Cheers,
Abel