Dahlem is a very safe district, and Berlin is actually a pretty safe city. You shouldn’t feel unsafe when walking home by yourself at night, even if there is no one on the street.
Unlike on many campuses in the United States and other countries, Freie Universität Berlin does not have its own security. There are no policemen, and there are no call boxes. The campus, however, like most of the city, is an extremely safe place during the day and at night. You should still exercise caution, especially at night, but you shouldn’t feel unsafe just because there are no guards around. You also benefit from the fact that in the summer it can stay light out until about 11 p.m.
Just in case you ever have an emergency, you should probably have the numbers listed on this link handy. In urgent cases please dial the emergency call number 110 (Berlin Police). The Berlin Fire Department is 112.
While Berlin isn’t exactly known for having very much crime, you should still be cautious. Berlin is a tourist city, and in the more touristy areas (such as Kurfürstendamm, Gendarmenmarkt, Brandenburg Gate, buses 100, 200, M 19, and M 29), you should keep a good watch over your belongings.
Another place to watch out for pickpocketing is when you are getting on or off a bus or subway, or going up and down subway stairs because then everyone is in movement, often brushing against each other, and skilled pickpockets can do their work and disappear into the crowd in a flash. Pickpocketing might also happen in pubs and clubs. Make sure that one person keeps an eye on your bags before you hit the dance floor or go to the bathroom.
If you don’t look white-Caucasian, try to avoid some areas in the East of Berlin, such as the Lichtenberg train station. These are a popular hangout for skinheads looking for trouble.
Many uncomfortable situations in the public transportation system in Berlin are harmless. For instance, there are often homeless people trying to sell street newspapers in the S-Bahn and subway. They usually give a short speech about themselves and then ask if anyone would like to buy one. These people are completely harmless, and you aren’t required to buy their wares.
In some train stations you can find many drunks and homeless people walking around. They are usually too drunk to cause problems, and the basic procedure is to ignore them. If you do run into problems, there is usually a good police presence to call for help.