Honestly, Catalonian food and sangria is all you need in life. Eating in Barcelona is a heavenly dream and the city provides an abundance of wonderful places to eat.
Here are some of my favorites, some personally discovered and many recommended by friends that have lived in the city:
La Boqueria Mercat
The famous market is a staple that you just can't miss. Located near the Gothic Quarter, it's a good place to stroll around and check out all the amazing seafood (who knew that people even eat fried barnacles?!), then find a place with an empty seat and eat some fresh tapas!
Els Quatre Gats
When I saw the menu with the caption under the patatas bravas saying, "the most badass patatas bravas in Barcelona", I was hesitant. I think IHOP also claims to have the most badass pancakes and...yeah. But, I tried them anyways. And the description is spot on. Els Quatre Gats can claim this title. The history of the cafe doesn't hurt your eating experience either: this used to be the social gathering spot for artists during the modernist period. Your blue man Picasso frequented here and his first solo art exhibit was on their very walls.
You have to go here for the margaritas and tacos. Hands down amazing. Located near the water, so you can take a stroll down the boardwalk afterwards to walk it all off!
A famous sea food restaurant that is almost impossible to get in. Get there early, don't stick to the normal Barcelona dinner schedule of 9pm. Make sure to follow up your seafood meal with shots of foam!
Located near the shopping area of Barcelona, Tapas 24 is spot on. I ordered their rabbit ribs and would've gone back again to eat them if I didn't have 30 more restaurants to try to get to! It is definitely a go-to place for future visits.
More tapas that friends recommended, but I was unfortunately unable to try:
Bar Canete, El Vaso de Oro, Lolita Taperia, and La Panxa del Bisbe
Moving on from restaurants to the good, sweet things in life:
Whenever I am traveling I like to grab a light breakfast that I can walk with while I continue on my touristic route. It's always a great addition when that light breakfast actually tastes good. In Hofmann's case, it is delicious. Hofmann is probably the best known pastry shop in Barcelona, known for their inventive stuffed croissants. There were undoubtedly be a line. It's worth the wait.
Satan's Coffee Corner
Located in the Gothic Quarter, half the fun of this coffee shop is walking there. But when you arrive, they have some pretty good coffee awaiting you!
You can't go to Barcelona and not head here. This is the place where cacaolat was invented. (Hey, don't worry, I never heard of it either before I visited Barcelona for the first time). Cacaolat is a chocolate drink that is microwaved and when it was created in the 1930s, it was the first bottled milkshake type drink. Besides their famous drink, they have some really good churros and other goodies!
My favorite wine & cheese shop in Barcelona. And, sorry Mom, everything I bought you has already been consumed....
Located near La Sagrada Familia, this is a good place to try some Vermut!
And always remember, when in Spain, service is notoriously slow. And I mean s l o w. There are actually a lot of problems within the Spanish industry/economy with this because people get so fed up with waiting, they often walk out on their bills.
So be patient, be persistent, and just enjoy your time there! Oh, and make sure to order the first time the server comes around :D