Some people ask me, where to find a good spot to have a great view to the stars. For Austria, this is a good link to follow. There are also a lot of other sites, just search for light pollution. There are also overlays for Google Maps here.
Light Pollution, taken from http://www.nightsky.at/
The second thing to remember is, that you need a clear sky and no clouds. Above 2000 m, the light pollution is at the most places acceptable and the air is thinner and also the lights of the stars brighter.
Third, you need a long dark time span. In winter you will find the perfect conditions. Also to mention: if you hear in the news, that a weather inversion takes place, get your car and find a hill. The air near the surface will be colder than in the highs and all clouds will follow the cold air.
Fourth: As i said before, find the highest place you can get! The air gets thinner, the stars become brighter. So simple, so good.
UPDATE:
Stephan Paukner from paukner.cc has also found some information and made a nice Google Maps overlay.
Dark Spots in Austria, taken from paukner.cc