An internet page of the German Railways (Deutsche Bahn AG) provides detailed information about train connections in Germany (and surrounding countries).
When checking the schedule, try to minimize the number of transfers (changes) and look at the total travel time (duration) which is given. Also the one way fare for each connection will be indicated. The webpage gives you three connections. Then you may add some earlier or later connections. The first page gives you just the time of departure and time of arrival as well as the number of transfers. You may then go to the page "itinerary" which offers more details on the transfers.
The trains marked IC or EC require a supplement of DM 7. The fast ICE trains, recommended especially when you go through Frankfurt(Main), have a special fare.
From Berlin
From the airport Berlin-Tegel, there is a frequent bus service X9 to Berlin's main train station Zoologischer Garten ("Bahnhof Zoo"). It takes about 20 minutes.
From the airport Berlin-Schönefeld there are trains every 30 minutes to Zoologischer Garten. They take about 20 minutes. (There are various other connections from Berlin-Schönefeld to Magdeburg that you may find. This would be too complicated to present here.) The last connection from Berlin-Schönefeld Flughafen is at 20:22 (excepting Saturdays when it is at 19:59).
From Zoologischer Garten there are direct connections to Magdeburg which take about 90 minutes. Most connections are direct, a few require a transfer in Genthin. The last connection leaves at 21:00 (excepting Saturdays when it is at 20:47).
From Frankfurt
From Frankfurt Airport it takes about 4 hours by train. Note that the airport has two train stations and make sure that you go to the right one for your connection. You take a train to Frankfurt(Main) Hauptbahnhof. From there one has two direct trains and many with a convenient transfer in Braunschweig. Depending on the time of day, you may wish to take another connection, but make sure that a later connection does not get you to Magdeburg faster.
When checking the train schedule make sure that you are NOT looking at Franfurt(Oder) which is east of Berlin. Also be careful that you do not run into a direct connection that makes a huge detour, is more expensive and takes 7 hours.
From Hannover
From Hannover airport there is a direct bus going to Hannover Hauptbahnhof. It takes about 30 minutes. Most connections are direct, a few require a transfer in Braunschweig. The travel time is about 90 minutes. The last connection departs at 21:29 (except on Saturdays when it is 20:28).
From Halle/Leipzig
From the airport Halle/Leipzig take bus line 300 directly to Halle Hauptbahnhof, 25 minutes of travel time. Do not go to Leipzig, that is a detour. (The latter does not mean that we would not recommend Leipzig, and Dresden, for an excursion on one of the days adjacent to the conference. We strongly do.)
From Halle it is about 60 minutes, depending on the train. All connections are direct. The last connection leaves at 23:23.