The first arrondissement which is referred to as the 1er is in the dead center of Paris. It revolves around Notre-Dame and the Louvre. The other 19 of the arrondissements revolve in a a spiral outward and clockwise in ascending order.
To find an address in an arrondissment is very easy. For instance, 77 Rue Cler, 7e, is in the seventh arrondissement. If you have a postal code of 75007, the address is in the 7th arrondissement. See, it's very simple. You'll find the numbers of the buildings to run parallel to the Seine - running east to west. On the North /South Streets, the numbering of buildings begin at the river. Here's how it goes:
Right bank: 1er, 2e, 3e, 4e, 8e, 9e,10e,11e, 16e and 18e.
Left bank: 5e, 6e, 7e, 13e, 14e.
OFFICE DE TOURISM: Hopefullly, you brought a map. But if you didn't and need information or a place to stay, you can stop at the Office of Tourism. For you return visitors, don't look for it on the Champs d'Elysees, the offices are now located throughout the city at 6 locations:
11 rue Scribe, 9e - Metro: Chausee d'Antin or Opera
18 rue Dunkerque, 10e: Metro and RER: Gare du Nord
20 blvdDiderot, 12e: Metro and RER: Gare de Lyon
21 place du Tertre, 18e: Metro Abbesses
99 Rue de Rivoli, 1er: Metro Palais Royal/Musee du Louvre
Eiffel Tower between the North and East pillars: Metro Bir Hakeim
Keep checking here, I'll have more details about the particular arrondissement at a later date. If you are interested in something in particular, just send me an email. If I don't know the answer, I'll find it out.