You basically have two options: an airport bus, which will save you some money but add time; or taxi, which is quicker but a little more expensive (an Away.com staffer cautions that you should "never accept a fixed-price taxi ride to his destination and always rely on the meter"). There's more useful info about transportation from GIG here: http://www.worldairportguide.com/airport/405/airport_guide/South-America/Rio-de-Janeiro-Gale%E3o-Antonio-Carlos-Jobim-International-Airport.html