You will propably arrive at the main station of Potsdam, "Potdam Stadt",
no matter whether you are coming in from Berlin (S-Bahn) or by train from
anywhere in Germany or Europe.
Just exit the station at the exit where the ticket office is.
Follow the only way possible up to the bridge, turn left until you see
the sign "606"
Bus 695
Exit the station at the exit were a sign says "Sanssouci".
Cross the area were the taxis wait.
The bus stop is on the other side of the road.
Tram
Exit the station at the exit where the ticket office is.
Follow the only way possible up to the bridge.
The tram stop is now right in front of you, in the middle of the street.
You can use every tram that heads to "Potsdam Pirschheide" or "Charlottenburg".
Exit the tram at the "Luisenplatz". Cross the "Luisenplatz". At the other
side of the square, turn left and head for the "Gruenes Gitter" (green
fence")
Taxi
Just follow the sign "Taxis", when you arrive at the station.