If you have the particularly first-world American problem of trying to find your way Europe, and then, say needing a place to stay while in Paris, don't worry: My friends in the blogosphere have got you covered. Here's some good advice from people who know what they're talking about.
Going to Europe in the summer is about as much as you can ask for out of travel. Most people will tell you to stay away during the tourist season, but if you want to be there when the weather is great, you’ll have to put up with some other Americans making you want to wear a Canadian flag pin.
If you're going to stay in Paris for a week or more, conside renting an apartment. Particularly if you're travelling in a group that would benefit from 2-3 bedrooms. Apartments are generally cheaper than hotels and integrate you more into the day to day life of the city.
I've never been to Paris, but I do hope to get there someday. Fortunately, I've got these links saved for future reference.