The Paris metro is a great, it is inexpensive way to get around and very easy to use. With a little planning you can see the whole city, only traveling by Metro, but a few things to keep in mind.
- If you are heading to Paris from the US, your credit card will not work in the ticket machines. (in fact US credit cards are a bit of a pain everywhere) The larger stations can have long lines to get a person who can swipe your card, so arrive in Paris with some change in hand to buy your tickets.
- It also helps to arrive with a metro map, even if it is a quick print out so you can get from your arrival point to your hotel. The stations do have maps and are well labeled, but when we arrived the paper maps were hard to find and it was reassuring when we were waiting on the platform to look at the map and know that we were in the right place.
- Buy the carnet - a package of 10 tickets - you will save money and you don't have to keep buying tickets. Since it is a pack of tickets you can split it between your group as well if you are only going to use the metro a few times. I believe in 5 days we went through two carnets.
- Some of the stations are very large with long underground tunnels and lots of stairs, not suitcase friendly. If you are a suitcase (vs. backpack) type, be prepared to be physically carrying your suitcase a lot.