Meals are almost always accompanied with bottled water. You'll be asked if you want con gas (carbonated) or sin gas (un-carbonated). Bottled water costs 3-4 pesos in restaurants. If you don't want to pay for bottled water, ask for agua de la canilla, otherwise known as tap water. To keep your water cold, ask for ice, which is only served when specifically requested. You'll be presented with a silver bucket filled with ice chunks and tongs.
In Buenos Aires, and in the rest of the country, beef is king, but it's not your only option. Italian food is pervasive but in neighbourhoods like Palermo, also popular are sushi, fusion, and even vegetarian bistros. Just about everything can be delivered - including gourmet helado (ice cream). If you're not vegetarian, try asado (beef/steak barbecue) at a parrilla, restaurants specializing in roasted meats. The bife de lomo (tenderloin) is comparable to European cuts. Jugoso means rare (literally "juicy"), however the Argentine concept of rare is very different from that of someone from the States. Don't be afraid to order azul (blue), you will not get a blue steak, but rather more a medium rare preparation. For rare steak ask your order to be prepared sangre (blood), or tell the waiter "me gusta sangre" (I like blood.)
Spanish food is also very common. Other popular meals are empanadas (small pastries stuffed with a combination of cheese and meats). They are a popular home delivery or takeaway/takeout option. Pizza comes al molde (cooked in a pan, usually medium to thick crust), a la piedra (baked in a stone oven, usually thin to medium crust), and a la parilla (cooked on a parilla grill, very thin, crispy crust). A delicious dessert is a cookie called the alfajor which consists of two round sweet biscuits joined together with a sweet jam, generally dulce de leche (milk jam, akin to caramel), covered with chocolate, meringue or something similarly sweet.
Smoking was banned several years ago in nearly all enclosed public places, including bars. The law is generally upheld, although larger bars ( more than 100 sq meters) are allowed to have separate smoking areas. The result is that smokers have moved outside. Bars in Buenos Aires have a very European atmosphere. They are the perfect place to read, surf the web, meet with friends, or just be a people watcher.