There are some things that I think are useful know to make sure you get the most out of your stay in Barcelona:
-Learn a bit of the language-
As always, it is useful to be able to read signs and so on, but more importantly some of the best food to be had is off the beaten track, where you'll find that menus are entirely in Catalan. Unless you're one for pointing and hoping for the best, some basic phrases are vital.
-Cover your shoulders and knees-
If you enjoy visiting religious buildings, take a wrap or wear a t-shirt rather than a vest if you're a lady and make sure your knees are covered if you're a man. With the weather being so hot in summer, it's sometimes not easy to do this, but you won't be able to enter unless you follow the rules.
-Get a 'tay day-oo'!-
The T-10 (pronounced as above) is a ticket for the metro and bus system that allows you ten journeys for around Euro7 (compared to the usual Euro1.10 per ticket). It is a single ticket that can be used by more than one person (just swipe it once for each person) and offers fantastic value. It's also valid for journeys to anywhere that I've mentioned in this review and many more within the zone and you can change methods of transport within 75 minutes of stamping the ticket.
-Watch the taxi supplements-
We got a taxi from the airport to our hotel originally and whilst it was a reasonable Euro28, we were shocked at the total. The taxis are all yellow and run on a meter. As we approached our hotel the meter read Euro20, however after a few button presses, we were charged a further Euro8! We later found out that this included a Euro1 charge per bag, a Euro3 airport surcharge and Euro3 extra because it was Saturday! There isn't anything you can do about it, but just bare it in mind before you exchange words with the driver.
-Keep an eye on your possessions-
This is generally a given when travelling, but during our stay we witnessed a couple of thefts, especially on the beach. From what we could see, the general modus operandum was to charge along the beach at break neck speed and just pick something up from an empty towel or unattended bag on the way past. The thieves, on all ocassions, where spotted by other members of the public and apprehended until the police arrives (which was always remarkably quickly) and the possessions were recovered. However, it does somewhat sour the experience and would have done even more so, had it been me that was the victim.