Don't spend a restless night at the youth hostel listening to Danish high schoolers extol the virtues of One Direction when you can score some solid sack time and make a new friend who, like you, hates One Direction, thanks to Roomsurfer: a free online service that connects travelers looking for accommodations with like-minded locals who share the same interests and hobbies.
Start by picking your city (they currently service five, including Berlin, Madrid, and Belgrade) and up to four interests, such as "Party", "Sports", and "Music". Their proprietary, NASA-esque algorithm will then incorporate your interests, likes, religion, favorite CD, whatever, into a precise search.
From there, RS matches travelers with hosts based on compatibility, allowing you to scroll through a list of people who also share your passion for collecting porcelain ballerinas and have a room/bed/couch for rent.
Prefer to bunk with an attractive woman in Barcelona who also lives near the Sagrada Família? Then you'll probably want to roll with the map view.
Meet Mariangeles. She looks pensive. Possibly angry. She may or may not want you to stay with her -- we can't tell. Either way, have a look at the bright yellow, 25€ private room in which you'll be sleeping, and the guitar you'll no doubt use to woo her with an acoustic rendition of "More Than Words".
Think you and Mariangeles will get along swimmingly? Well then, become a part of the "magic" by logging in via Facebook and booking your stay through PayPal.
More of a visual learner? Then watch this vid explaining the whole process through the use of nifty graphics!