Hooking up the Internet

The first thing you need to do before getting internet is to get a landline with national former monopoly France telecom*. In France, a landline can be distinguished from a fixed-line (or téléphone fixe) in that the former is very expensive to make calls while the latter can be free. For fixed-lines, most go with either free or tele2, who offer more attractive rates. Keep in mind that even though fixed-lines offer free calling to several countries, calls to mobiles are almost always not free, even if they're French mobiles.
If you have chosen to go with a company other than France telecom's internet service provider, Wanadoo, simply decline any offers because salespeople in France can be especially pushy and France telecom does not offer very good rates to individuals.

Here's a list of broadband providers in France courtesy of Birds-Eye.Net.

*You might need to contact your landlord to get the previous phone number that was attached to the line.

UPDATE: Most Internet services in France are pretty hit-and-miss. It is rare that you will ever get a unanimous recommendation. Recently, some friends have had big-time problems with Free, including my roommate who has just switched to Club Internet.