Enjoy your time there. I go to BCN atleast 2 times a year for pleasure sometime more..
Best web site I have found for hotels is
http://www.booking.com
Enter the destination and date, for Barcelona are three choices pick Barcelona city
There is a city map so you can get a place around where you want, without looking at a hotel then try to find it's location.
Also there are reviews from past travelers.
For New Years I stayed at Hotel Bel Art and a buddy at Hotel Medic. These are just 3 blocks above Cathedral La Sagrada Familia, and only 1 block from the subway.
Get a day pass or week pass on public transportation. Clean, safe and cheap!!!
If you get a chance take the train to "Monistrol De Montserrat". Just before this town is the stop "Pont De L'Aeri"
From here you can take the cable gondola up to the monistary Montserrat. All I can say is breath taking and amazing!! Try to go on a day with good visibility.
Places to eat:
On the beach prominade walking from Port Olympic North, just past the Mc Donalds you will see "Escriba" great for big meals.
Tapas.. near the intersection of Rambla de Catalunya and Carrier De Mallorca find Cervezaria Catalanya, best tapas in BCN. If you get there after 8 expect to wait 1-2 hours for a table, reservations not taken.
Have fun.