I would like to thank Bahrain Lad and Helsinki Flyer for your comments. I am amazed that people are actually interested in reading this. Like I have said in my first little blurb, I am just trying to help those who are inundated with having to travel in Europe and don't necessarily have good background information. I am now just trying not to screw up.
That said, I'll start my blurb on city transportation here in Germany but I think this would be good for most cities in Europe. After an airline commute, most American business folks head straight to the rental counter or a taxi. I covered the rental counter in a previous section. Taxi's in most major European cities are widely available at the airport, major rail points and some attractions like a group of museums (Berlin's Museum Island for example). In Germany, you can find rates posted somewhere within view of the extrior of the taxi, not necessarily posted on the door like NYC but I have seen a few. I haven't taken a taxi here in Germany but I imagine that it is as much a crap shoot as in the US. Some are good, some are bad. I have heard good things about Taxi's in London (the 60 minutes report comes to mind) but I haven't been able to verify this yet. I'll give it a try when I'm there.
Outside of Western Europe however, everything I have read says that you should be extreamly cautious about them. Prauge and Budapest taxi's are notorious about taking tourists for the proverbial "ride." There is a line of thought that you should barter with the taxi driver prior to even getting in the cab. If you speak the language, by all means, give it a try. For english speakers, it may not be worth the hassle if you get a particularly bad driver. If someone is trying to take advantage of you, your best option is to walk away if possible.
The other option that many Americans never try is the mass transit system. Many European cities do have their transit systems running into the early morning hours EXCEPT France!, well Paris at least. I got a bad report yesterday that my co-workers in Paris had to walk back to their hotel after being out until 1AM. Not the best experiance with mass transit as they like driving everywhere. There are even good systems in even medium size cities like Mannheim or tourist areas like Heidelburg. Granted, you may be better off walking in these areas but know where the tram lines are for a faster way to get to a meeting.
Mass transit in Germany usually includes both bus and tram routes. Major cities have some subway systems. Berlin, and I imagine others like Frankfurt and Hamburg, have all 3 networks. Berlin's is massive and extends from Potsdam all the way to Neuenhagen I believe. You can still tell where the wall was and the city has been really good about a small line of cobblestones and markers demarking exactly where the outer wall was. For those who don't know, there was an outer wall, the one with all the graffiti, a deadman zone and then another wall. Much of the wall zone is now being filled in with apartments and such. <<Notes on this later>>
Berlin's system is under constant construction with the major area being Potsdammer Platz, where Hitler's bunker is now under a nearby parking lot unless they removed it. I was amazed at the growth as I was there in 1994 when there was just dirt, dirt, and some rubble piles and a free standing section of Wall. The major transit lines are Charlottenburg to Ostbahnhoff (4 lines each plus others) and a city ring line consisting of 3 to 5 lines. Berlin's maps are confusing as there are 2 of them. One shows the U, for Unterbahn (I know the Unter part is right), system and then an S for Stadtbahn.
The confusion comes in as the maps can overlap on each other so you have to know which one you are looking at. The nasty part is that they can be displayed next to each other in most stations. The best way to tell is to look for "grayed" in areas around Bahnhof Zoo or FriedrichStrasse. The grayed in areas on this map will show the U system. I haven't seen any U system maps with the S system grayed in, they are usually running on top or with the U line. Many stations will have a yellow circle around the station you are at or a red arrow which can definatly help when trying to make a connection. I think most know how what a subway line is so I won't go into that.
Alright, now we come to fares. Many fares are available through the machines at all rail stations. The nice city government of Berlin has issued touch screen machines that are available in the major languages. I believe they did this to eliminate any excuse for tourists to say, "I didn't know what da machine told me". According to my reading material, it's a 40 euro fine to be found by your neighborhood metro politzi (police). You are definatly better off just buying a ticket as a 3 day all area pass is 22 euros. There are 3 areas to the Berlin system called A, B, and C (I know its complicated). Most of the attractions and business points will be in A but if you have to go to Potsdam, that is in C and the Olympic Stadium is in B I believe (my map in front of me is not as extensive as others).
The most common fares are a Point to Point, PTP or a timed usage pass from 90 minutes to a Day Card. In ALL CASES, tickets must be validated when first used, this goes for Day and MultiDay tickets as well. If you don't do this, your neighborhood Euro collector will be more than happy to help you after you paid him (granted he must find you first). If he just validates your ticket at the next stop, consider it a warning and say Vielen Danke.
In the major cities and most smaller ones, it does not pay to do PTP unless it is less than 2 Euros, which I have never seen in my short travels (you'll see why in a minute). There are strap tickets, which are good for a certain number of trips. To use these, you will be given a strip of tickets at the time of purchase. When you want to use the system, tear off a ticket and VALIDATE it. Depending on local rules, you may have to use another ticket to go the opposite direction.
The option I use is the Day Card or Day Pass (Tageskarte). This way, I don't have to mess with validating, knowing zones (unless I wanted to go to a stadium or was being cheap), or messing with a machine late at night. These passes can cost between 5 to 7 euros a day and larger cities like Berlin offer multi-day passes for tourists. I buy my ticket, turn to my left or right where the validating machine is and VALIDATE. I don't mean to be your mother on this one but 40 Euro is 40 Euro, plus think of how much garbage you will receive if someone finds out. If you are interested in seeing more of the city in your time off, these can be a good deal. Depends on where your hotel is and how much walking you want to do. Definatly ask the front desk or a waiter/waitress for offtime activities or use reading material eg. books.
The last items are bicycle(bike) riding/walking. These two can be the healthiest and best ways to see the city, provided you pay attention and the nearby drivers follow traffic symbols. Bikes are available at almost every major rail station and many hotels have them available for rent/free loan or know of a place that has them available. I'm from Denver so biking to work is a very normal thing to do for me.
The red paths painted or stone work are bike lanes and many cities have been good about installing them in major routes. Many pedestrians have been good about getting into the lanes and getting in the way of a bicyclist. Try to stay out of the bike lanes if you are on foot as sometimes the bicyclists don't look for you either. If you hear a bell, that would be a bicyclist telling you to either get out of the way or letting you know where he/she is. I try to stay out of their way as much as possible but sometimes you just get stuck and can't get let them through. I've been fortunate to not get run over. Appologize and let them by as most of them are just like you, trying to get from A to B. Your mother will be proud of you if you wear a helmet and many rental places will provide them with a rental.
An interesting note from Berlin, the Deutche Bahn has gotten into the bike business. I have seen numerous DB bikes for rent around town in all the touristy places. I haven't been in a major city until now so this may be a trial or an expanding program. It looked like the bikes had an electronic lock on the chain but I will investigate this matter and report in the future.
As for walking, it is definatly the cheapest way of moving around a town. You will probably find your restauarant for the evening by walking your neighborhood around your hotel. I stayed near the Charlottenburg station in Berlin and felt safe walking around even with a small red light area outside the station. The barkers for the strip clubs were interesting but are quiet if the club is full of patrons on Friday, Saturday or Sunday night. Monday night - look out. Walking is also a way to stay healthy and walk off all the dinner you ate way too much of or the breakfast buffet that was so filling you shouldn't even think about lunch.

I really need to make these posts smaller, sorry about the length and keep sending in comments or any questions I might be able to answer.