What is the best way to book tours or site see when I get there. We are also staying for 4 nights what are fun things to do there?
Barcelona is a city with a variety options to see. You can look for free tours in Google and will show you different companies that offers free tour in the city. In the end you can pay what you considers. Remember give something in the end for each person.
In Barcelona the most famous is Sagrada Familia, Park Güell, Barceloneta Beach, Montjuic, LA Pedrera and to get lost for Gracia (an independent area in Barcelona)