Buenos Aires isn't exactly a very safe city so its important that you slightly blend in with the locals to avoid being easily noticed and targetted by pickpockets. Here is how you can easily blend in among the locals.
Don't go texting on the streets. This will easily make you stand out.
Keep change- coins are hard to find due to inflammation but still very important since you need for minor expenses such as bus fare.
Tipping - it isn't mandatory but its sort of the norm in restaurants and pubs.
Dinner is taken late- most Buenos Aires locals take dinner past 9 pm.
Carry your camera in a bag and only take it out for taking photos.