This page has some tips of how to find accommodation in Barcelona for students. I've been there myself and learnt all the tips to ensure you can find somewhere fast, cheaply and that meets your needs.
Finding shared accommodation in Barcelona can be quite tricky because there is a shortage of shared accommodation here but if you follow these strategies you'll have a very good chance of finding somewhere that meets your needs quickly.
The first thing you should do is get yourself booked into a youth hostel. This offers a cheap form of accommodation, usually shared with other students, who are in the same boat as you and it's a great place for you to make initial contacts with people.
Start your search for youth hostels in Barcelona.
If you fancy having your own room and you don't mind paying a little bit more then you could probably try renting a room in a hostal. During off-peak season you could probably find a room for around €15.00 to €25.00. One place to try would be Europa Hostal.
Calle Boqueria, 18
Tel: +34 93 318 7620
Metro: Liceu (Green Line, L3)
You could probably find a single room in off-peak time for roundabout €18.00 per night.
The next stage would be to make your way to the students advisory office CIAJ:
Sant Oleguer 6-8
Tel: +34 93 442 2939
This office is a government organization that gives general advice to young people.
Important Note: For legal reasons CIAJ no longer have advertisements for accommodation either in their office or on their website.
I strongly advise that you do not go to any agencies that claim that they can find you a flat or a shared room in a flat for a fee. There are dozens of agencies like this around Barcelona and I have known many, many, people who have paid good money and never received anything of any value. Usually all you will get is an outdated list of flats that have already been rented.
My advice is do not go to these agencies. The only time it might be worth considering an agency is if they do not charge you until you have found a place. There are government officially registered agencies that can do this but normally they only deal with long term rentals and not flat shares.
Be wary and use your common sense when looking for a place. There have been a lot of cons going on where students have paid a deposit for a place, turned up on the appointed day only to find a whole bunch of other students have also paid a deposit for the same room. The "owner" had not been the real owner and had played off several unsuspecting students to get their deposit money. If you feel that something is not right, it might be better to walk away.