Because Atlanta is a continuously growing, sprawling city, many residents in the metro area rely on cars to get around. But for tourists remaining in the city center, Atlanta's primary public-transit operator, MARTA, is a good way to literally go — you can traverse most of the city this way.
Public transit
Atlanta is serviced by the Metropolitan Atlanta Rapid Transit Authority — MARTA for short. While it began as a bus system, it now has 38 train stations across Atlanta, plus an easy-to-use, low-cost airport shuttle. Rides cost $2.50 each way with four free transfers permitted within a three-hour window. When I was a visitor I used to hop on frequently as a quick way to get to my friends' places in midtown.
The airport station, part of the red and gold lines, is in the domestic terminal's baggage claim. If you're coming off an international flight, you'll want to take the free shuttle, which will drop you off at the baggage claim, where you can hop on the train.
If you plan on using the MARTA system, you can purchase a Breeze Pass for one, two, three, four, seven, or 30 days, or punch cards for 10 or 20 rides. The red and gold lines mostly run north and south, diverging past midtown to go to Buckhead and OTP to Dunwoody and Sandy Springs (red) or to Lenox, Brookhaven, Chamblee, and Doraville (gold). The blue and green lines run east to west for easy access to midtown, downtown, and neighborhoods like Five Points, Inman Park, Edgewood, and Decatur. All trains run about 20 minutes apart.
MARTA also has a streetcar that runs every 10 to 15 minutes; it costs $1 to ride with no transfers or $3 for unlimited rides within 24 hours. This route doesn't cover a large distance and mainly stays downtown, circling from the Peachtree Center near the Centennial Olympic Park and the CNN Center to Sweet Auburn and Georgia State University.
Finally, you can take a MARTA bus. This enormous network extends well beyond the perimeter in several directions. Access is covered in your Breeze Pass, too.
Rental car
In such a car-heavy city, there's a wide selection of wheels to choose from. Offices for Sixt, Enterprise, Avis, Budget, Thrifty, Hertz, and more are scattered throughout the metro area for easy pick-up or drop-off. Several of these providers also offer reservations so you can pick up your ride at the airport.
However, while driving is the most flexible way to get around the city, it may not be your best choice. Parking availability varies by neighborhood, but it's never truly plentiful or free until you enter the suburbs. Atlanta traffic is notorious, and the supersized highways are frequently bogged down with heavy construction, poorly marked signs, sudden lane endings and merges, and changing exits as cars and big rigs make their way through the city.
Ride-hailing services
I'm a big fan of Uber or Lyft as a method of getting around Atlanta. Rates have gone up — but, to be fair, so has fuel. To me, splitting the cost with your travel companions to ride in comfort without having to brave the chaotic interstates yourself is invaluable, and having a designated driver after having yourself a good time in Atlanta's glittering nightlife scene is always a good idea.