Make all reservations in advance here in states like travel for trains and planes. My daughter had one semester of german and we thought we wouldn't have problems getting on train but they speak german and if you only speak english you will have a problem communicating where you want to go. I was trying to play it by ear but my daughter and I got on the wrong train going to wrong way as we were trying to get to munich and had to get off the train and switch to another train going to right direction. Also the tickets you buy there are only good for a specific train as there are fast trains and slow trains. If you buy your tickets here first they are good for either train the fast more expensive or the slow ones. Trains leave every 20-30 minutes almost anywhere in Europe but getting on wrong train is upsetting especially if you are trying to check into a hotel by 6pm or they rent it to someone else.
At night women should not take all alone the public transport. Take taxis or stay together with other. Don't take late in the evening the U-Bahn. - I just mean to say: be careful, not forgetable. :o)