Around the Mercedes-Benz Arena there's lots of parking space. There are free car parks along the Mercedesstraße, which runs along the stadium.
By public transport: Take line S1 of the S-Bahn from the Hauptbahnhof of Stuttgart in the direction of Kirchheim and get off at Neckarpark, a ride of just under 10 minutes. From here it's a couple of minutes walk to the Mercedes-Benz Arena. On match days also special metros run to the stadium, line U11 to Neckarpark (Stadion).
The fastest way to your seat depends of where your seat is: From the Untertürkheimer Kurve, the Gegentribüne or the away end the station of the S-Bahn is nearer, for the main stand ant the Cannstatter Kurve the stop of the U-Bahn is closer.
About a 20 minute walk from the Mercedes-Benz Arena is also train station Bad Cannstatt, where mostly regional trains just as the S-Bahn and U-Bahn have a stop.