hidee ! born and bred in germany here, karlsruhe area (baden-württemberg).
like mentioned by other users before, hochdeutsch=highgerman is the way to go.
it is official language used for government, police, official statements, in education, newspapers and writing.
any schoolbooks u buy, grammar, didactics, vocabulary will be in highgerman automatically.
then theres the dialects. they are not written, but spoken, there are so many different dialects, i once coming back from an interrail trip stopped every 40 minutes on a trainride, and the peoples dialect had changed !
the most significant dialects are bavarian, swabian, saxon (really ugly lol), the swiss of course with their embarrassing way of talking, and the austrians do their thing too.
try find some soundsamples on the internet, and heres a map too...
http://upload.wikimedia.org/wikipedia/commons/5/5b/Continental_West_Germanic_languages.png
(by the way i am 27 on that map...)