Paris is not an huge cities, but it will take you 3 hours of walk to cross it part to part.  Here are some ways to visit without killing yours feet.

Metro and Bus
The most easy way of visiting Paris. Our city have one of the best subway of the world. It deserve all the area in Paris. Check here for more information on how to use it.

Taxi (soon)
ah french taxi, some goods tip to keep a good « souvenir » of your trip in Taxi in paris

Velib (soon )
Rent a Bycicle for a few euros, an ecologic and easy way to discover the city of lights.