For mid-range prices, but good quality, stay out of central (ie "arrondissment") Paris. The public tranport is good and cheap, and you can have a higher quality stay, for less money, but you'll be jumping on a train for 15/20 minutes to get in and out of the central area. The Hotel du Lac at Enghien les Bains is a great place as a base, and is only 4 stops north of the Gare du Nore. Good Bistro style resturant in hotel, but can be a little expensive if you're on a lower budget, and get carried away with the wine etc. It's obviously more convienant in Central Paris, but you'll pay for it.