To get there, take the U- or S-Bahn to Ohlsdorf and change to Airport Express bus N°110. A €2,50 single ticket is required for the trip. Allow a half hour travel time from the ciy centre.
Alternatively, hop on the Airport Express bus directly from Hauptbahnhof station to the airport. Tickets are €5 (children €2), €4 if you're in a group of six or more. Buses depart at 04:40, 5.00, 05:15, then every 15 minutes until 19:00, then every 20 minutes until 21:20.