Before leaving for the large Spanish city of Barcelona, try to consult the Tourism site of Barcelona which will give you all the information you are looking for on accommodation, things to see and do.
In case you are already in the charming Spanish town and you cannot or do not want to waste time in front of a PC, go directly to one of the many tourist offices, there are many: Sants Estaciò, open every day except Saturday from 8 am to 20 pm, on Saturdays it closes at 14 pm. Closed on 1 January, 25 and 26 December.
Placa de Catalunya 17 S (in the basement), open every day from 9 to 21. Closed on January 1st and December 25th. On the corner with Placa de Sant Jaume, open every day from 10am to 20pm, until 14pm on Saturdays and public holidays. It is closed on January 1st and December 25th. Near the Sagrada Familia, open from the end of June to the end of September from 10 to 22 in the evening, every day.
If, on the other hand, you don't want to bother to look for one of these information points, beware of the magazines you find on buses and subways. Microphone, is a pocket-sized monthly magazine on everything that happens in the city, to be jealously guarded in the bag and to be consulted to decide the evening. B-guided, is a useful and nice guide, full of guides on all topics: b-inspired, b-ing, b-wear, b-seen, mainly oriented on design, music and clothing.
AB, a very popular magazine among the people of Barcelona and very useful. To complete the picture, I just have to recommend the Barcelona Card, valid from 2 to 5 days which offers numerous reductions, from museums to shops, restaurants, and more importantly, unlimited travel on subways and buses.