The Guia T will not only let you catch the right bus, it's a great pocket map. Also available in pocket size is the Guia Filcar.
On Foot
Your best bet is to buy a street map, but if you are online the best map we've seen is here. Taxis
Be sure you take "radio taxi". These are the safest taxis as they are legitimate. It should cost no more than $15-20ARS to get anywhere in the city.
Subway
The Subte (short for Subterraneo or Underground) travels to just about every corner of the city. For more information on ticketing and getting aboard see this video.
Buses
Local
Use the Guia T to find your way around all of Capital Federal. The buses are safe and run regularly.
Long Distance
Go to the bus station in Retiro. There are buses to every part of the country leaving every few minutes and even up to Brazil or across to Chile.
Trains
Local
There are several train stations throughout the city that will take you to the suburbs of Gran Buenos Aires.
Long Distance
For trains down to Mar del Plata and other southern destinations, trains make a great way to travel.
Airlines
International - If you have a trip planned outside of Argentina you will need to fly out of Ezieza, the airport where all international flight arrive and depart. It can take up to an hour to arrive from the city to this airport, so plan ahead.
National - We recommend using Asatej Viajes for your natioanl travel arrangements. They have multiple locations within Buenos Aires and are efficient. National flights depart from Aeroparque Jorge Newberry, located within the city.
Ferries
For a quick trip to Uruguay, you can't beat the ferry across the Rio de la Plata. There are two options:
Fast
Slow