Having lived in the “vingtième” (20th arrondissement of Paris) for a year and a half and spent about a quarter of it underground and on trains, trams, buses and bicycles, I think I’m fairly well placed to offer a few bits of advice about getting around the city. Firstly, travelling around Paris can be complicated. The French way, or specifically the Parisian way of imagining, signing and realising transport networks is different to most. Sometimes, bafflingly so. They’ll try and perplex you with symbols and the Paris transport chiefs will always do their level best to give a station two or three different names depending on which bit of it you want and how you want to use it. The most notable example is the famous Gare du Nord, from where it seems you can travel nearly anywhere, even to Britain. But beware because it might be that you want Magenta if and only if you require line E. There is of course the tube which is helpfully called Gare du Nord. Although, should you want to travel to other parts of France you’ll need the mainline in the main body of the station – downstairs though, not upstairs as that’s for the Eurostar – and then just one more decision, is it a TER or a TGV train you’ll be needing? Oh and I nearly forgot. Attention! Because some tickets you will have to “composter” at the little yellow machines, though sometimes they’re silver and blue, on pain of, well, no-one quite knows what happens to folk who don’t pre-punch their tickets. Of course, suffice to say, some tickets, and you never know which ones, are “déjà composté” (already punched) so it would be sheer folly to try and do it at the machine as this would not only invalidate your ticket but the machine would blow up and you’d have some serious explaining to do. Finally however, you might be getting a regional train (an RER), which is like the trains at Magenta but for lines A,B,C and D. They’re also slower and dirtier. Oh, and in a slightly different place.
So to sum up. My advice would be to stay perfectly still and don’t move. But if you do have to move about, take the metro. It’s cheap, frequent, each line has a colour and number, it’s open til well past a decent chap’s bedtime and you don’t need a degree in deductive logistics to work out the metro maps. Or you could take the nice new leisurely trams and actually get to see, what is after all a very beautiful city.