Metro stations can be recognized by the blue sign with a white U ("U-Bahn") on it.
Upon passing through the ticket barrier, you need to validate your ticket by inserting it into the blue ticket punching machine. Tickets that are valid for more than one ride need only be punched on the first use. Weekly or monthly travel passes need not be stamped at all.
On the platform, check the platform indicator to make sure you are boarding the correct train. Trains are indicated by their terminus, and the indicator also shows how long you have to wait for the train. On the picture below, a train to Seestadt will arrive in 1 minute, followed by a train to Aspernstrasse in 6 minutes.
Once the train arrives, the doors do not open automatically. You must open the door yourself by either pulling the handle or by pressing the illuminated button.
On leaving the train, check the overhead station name signs for the exits. Exits are always marked in white letters on black background. Be aware that most stations have two exits; on the street level these can be more than 300 metres apart, so picking the correct exit is absolutely crucial. If you want to change to other metro, tram or bus lines, make sure you take the exit marked with the respective underground, tram or bus symbol.
In case of emergency, look out for the illuminated SOS sign. There you'll find an emergency telephone, a fire extinguisher and an emergency train stop.