Take the S7 to station Wien-Nord/Praterstern. The Prater is within 200m from the station. The S7 drives regularly, please check www.oebb.at for exact departure times.
Leave the airport area and follow highway A4 for 13 km. Leave the A4 at Prater. Follow Schüttelstraße for 2.5 km, turn right onto Franzensbrückenstraße and follow it until you reach the roundabout. Take the second exit to the Prater.
If you arrive by car: this area is a short-term parking zone. Please buy a prepaid parking voucher at a local tobacconist (€ 1,00 per hour - as per 1st of May 2012). Additionally you can find a variety of charged parking areas.