By plane at Leipzig-Halle airport
After arrival at the airport, look for signs to the airport train station. If you feel it's a long walk - then you are on the right track! Direct trains to the main station ("Hauptbahnhof") in the city center run every 30 minutes.
You can buy your ticket either at a ticket counter (still in the airport building) just before you move down to the tracks, or downstairs at a ticket machine. Tickets for the regional trains ("RE") are also valid for changing to the tram at Hauptbahnhof (at least within the city limits). Long distance trains ("IC"), which also every now and then connect the airport with the main train station, require a special, much more expensive ticket (which furthermore is not valid on the trams from Hauptbahnhof).
For directions how to get from the main train station to the conference site, read on.
By train at Leipzig main station
From the main train station ("Hauptbahnhof", number on the map below) take the tram no. 15 in direction "Meusdorf". After a 7 minutes ride get off at the fourth stop ("Ostplatz", number on the map). From there it is a short walk to the conference site ("Linnéstr. 5", number on the map).
With only four stops, you can take a "short-ride ticket" ("Kurzstrecke") or just use your RE train ticket from the airport. General information on the Leipzig public transportation system and schedules of tram and bus lines can be found here.
From the north: Take the freeway ("Autobahn") A9 in direction Munich until "Schkeuditzer Kreuz", then the A14 in direction Leipzig/Dresden. Exit at "Leipzig-Mitte" and take the highway B2 towards the city center.
From the south: Take the freeway A9 in direction Berlin until the exit "Leipzig-West". Then follow the signs to the city center.
From the west: Coming from the Frankfurt area you are following the A4 until "Hermsdorfer Kreuz", where you change to the A9 in direction Berlin and follow the description "from the south". Coming from the Hannover area you are on the A14 in direction Dresden. After passing Halle and the "Schkeuditzer Kreuz" you can follow the description coming "from the north"