Know your destination; follow the right line.
Having only experienced the underground in South Korea with a chaperone I was somewhat daunted by the prospect of using the Underground/Tube/Metro in London and Paris.
After my first mishap on the first Sunday where I seemed to go around in circles and wondering if I would ever see the light of day again I was terrified about going into London on the 11th and making my way to Madam Tussauds.
Turns out, I was worried about nothing.
The trick is in both London and Paris is to know the destination of the tube and work back to your stop from there. Paris has been slightly trickier as the stops are all in French; and rightly so.
I have found that Google Maps have been invaluable about getting from A to B or giving a general idea. Also, people are very helpful if you look a little lost.
Also, I had some great notes about how to get around Paris from my friend Caroline.
So, all in all.... not so scary after all.