Argentinian breakfasts are somewhat light compared to what travellers from English-speaking countries are accustomed to. Typically, they consist of a hot drink coffee, tea, milk with some toast, medialunas croissants, literally "halfmoons", or bread.
Hotels typically provide a free buffet consisting of coffee, tea, drinkable yoghurt, assorted pastries and toast, fruit, and perhaps cereal. These kinds of breakfasts are also readily available in the many cafes.
Lunch is a big meal in Argentina, typically taken in the early afternoon. Lunch is so big because dinner is not until late: 20:30-21:00 at the earliest, more commonly at 22:00 or even later. Most restaurants do not serve food until then except for pastries or small ham-and-cheese toasted sandwiches tostados, for afternoon tea between 18:00 and 20:00. Tea is the one meal that is rarely skipped. A few cafes do offer heartier fare all day long, but don't expect anything more substantial than pizza or a milanesa breaded meat fillets or a lomito steak sandwiches outside of normal Argentine mealtimes. Dinner is usually eaten at 22:00 and typically consists of appetizers, a main course, and desserts.
By the way, North Americans should beware that Argentinians use the term "entrée" to refer to appetizers. This is common outside of North America but can surprise some Canadians and most Americans. Only in North America outside of the province of Quebec is the "entrée" a "main dish". In Argentina the main dish is a "plato principal".
The entrée in Argentina typically consists of empanadas baked pastries with a meat filling, chorizo with bread this is called a choripan, the most common street snack or morcilla meat or blood sausage, and assortments of achuras entrails. For a main dish there is usually bife de chorizo sirloin / New York Strip steak and various types of salads. Dessert is often a custard with dulce de leche and whipped cream topping.
Beef is a prominent component of the Argentine diet and Argentine beef is world-famous for good reason. Argentina and Uruguay are the top 2 countries in the world in consumption of meat per capita. Definitely check out Argentine barbecue: asado, sometimes also called parrillada, because it is made on a parrilla, or grill. There is no way around it - foodwise Argentina is virtually synonymous with beef. The beef is some of the best in the world, and there are many different cuts of meat. Lomo tenderloin and bife de chorizo are excellent. "Costillas" ribs is considered by locals the real "asado" meat cut and is very tasty. North Americans will see that costillas are different to those at home. Argentinians cut ribs perpendicular to the bone. Having a parrillada dinner is one of the best ways to experience Argentine cuisine; preferably with a bottle of wine and a good amount of salads. In some popular areas, parrilladas are available from small buffets, or sidewalk carts and barbecue trailers. Skewers and steak sandwiches can then be purchased to go.
Given that a large portion of Argentines are of Italian, Spanish and French descent, such fare is very widespread and of high quality; pizzerias and specialized restaurants are very common. Argentines take pizza seriously and consider their pizza to be better than Italian or American pizza. The standout characteristic of Argentine pizza is the excessive amount of cheese in the pizza, usually not with much sauce and a very thick base thinner bases are also commonly found depending on the pizzeria. You can order by the slice and eat standing up or order it whole at the table. Take note that a convention observed in Argentina is to treat the pasta and sauce as separate items; some travellers have found out what they thought was cheap pasta only to find that they were not getting any sauce. You will see the pasta for one price and then the sauces for an additional charge.
Cafes, bakeries, and ice-cream shops heladerías are very popular. Inexpensive and high-quality snacks can be found in most commercial areas, and many have outdoor seating areas. Empanadas turnovers containing meats, cheeses, or many other fillings can be bought cheaply from restaurants or lunch counters. The Alfajor is a must try snack of a two cookies with a dulce de leche filling and can be purchased at virtually any local kiosco. Every local have their favourite Alfajor brand but one of the most popular may be Havanna which is also a coffee house chain or Argentina's Starbucks, and also sells their famous alfajores.
Heladerias in Argentina are generally of good quality and are almost similar to Italian gelato in texture and flavour. Popular high-end but also high quality chains are: Persicco, Freddo, Volta. There are cheaper chains like Grido but is usually considered as sub-par ice cream. There are also many individual artisnal helederias which make good helados. An Argentine idiosyncrasy is home-delivery ice cream. It is not uncommon to get home-delivered ice cream at 3am!
Smoking is now prohibited in most Buenos Aires' restaurants and all of Mendoza's restaurants. In some cities, it´s forbidden in all public buildings cafés, shops, banks, bus stations, etc, so it´s better to ask before smoking anywhere.
Tipping of 10% in restaurant is customary and expected, even if the bill includes a service charge and a table charge. Usually only applies to sit down restaurant with table service.