Paris has an excellent range of hotels to suit nearly every budget, from the opulence of the famous hotels such as the Ritz, down to the armies of smaller hotels across the city. It is normally worth booking, especially if you're looking in guides. Hotels with good publicity (in print or on websites) tend to book up quickly and early, so you should get in there first. If there are two of you, it often makes sense to find a hotel room rather than taking two beds in a hostel - it can typically be cheaper and afford more privacy.