Paris is without question best explored on foot, and thanks to Baron Haussmann's mid-19th-century redesign, the City of Light is a compact wonder of wide boulevards, gracious parks, and leafy squares. When you want a lift, though, public transportation is easy and inexpensive. The métro (subway) goes just about everywhere you're going for €1.70 a ride (a carnet, or "pack" of 10 tickets, is €12.70); tickets also work on buses and trams and the RER train line within Paris.
Paris is divided into 20 arrondissements (or neighborhoods) spiraling out from the center of the city. The numbers reveal the neighborhood's location and its age, the 1er arrondissement at the city's heart being the oldest. The arrondissements in central Paris—the 1er to 8e—are the most visited.
It's worth picking up a copy of Paris Pratique, the essential map guide, available at newsstands and bookstores.