Well I think it's wise to try to see a few things rather than be running from place to place. You'll be jet-lagged when you get in, and probably arrive fairly late in the day, so figure you're really going to have three full days. I'd just concentrate on a nice dinner your first night, maybe a few drinks, and get some sleep.

Your first visit should include some time exploring the Ramblas and the Gothic Quarter. Starting at Plaza Catalunya, you can walk down the Ramblas, do some shopping, stop for tapas a half-dozen times, and wander around the little alleys and passageways of the Gothic Quarter. Realistically, this is a full-day's activity. If you get a really early start, you can probably fit in something else - maybe in the afternoon (after 5) go check out La Padrera, one of Gaudí's most beautiful and interesting buildings. It's at the cornder of Passeig de Gracia and C/Aragó, about a ten-minute walk from Plaza Catalunya.

Your second day, go get on the tourist bus. It leaves from Plaza Catalunya about every half hour. They go to all the tourist attractions, explain things in English, and let you get on and off as much as you want - just hop on the next one when you're ready to leave. This will give you a pretty good overview of what there is to see. On your third day, go back to one or two of the things you really liked and spend the day. I don't think you're going to have time to see the country, honestly. If you really want to, make your third day a daytrip to Montjuic, which is about 90 minutes by train. It's an old mountain monastery with a breathtaking church and views you won't believe.

As far as hotels go, the Calderon is my favorite in the city. Fantastic. Ask for a corner room - you'll give up the terrace but get a much bigger room. And don't miss the rooftop pool - it has some of the best views in the entire city. The hotel is also about a 4 minute walk from Plaza Catalunya, where all the fun starts.

Hope this is some help.