The Akihabara Convention Hall venue is located directly in front of JR Akihabara Sta.

Akihabara Daibiru, 1-18-13 Sotokanda, Chiyoda-ku, Tokyo 101-0021 Japan

If you are travelling directly to the venue, the Keisei Skyliner (train) is recommended.
Take the Keisei Skyliner to JR Nippori Sta. (JR Yamanote Line) and the JR Yamanote Line to JR Akihabara Sta. (3 stops).
70 min./ 2,070 JPY.

Depending on your hotel location, the Narita Express (train) may be the best choice for transport to central Tokyo (53 min/ 2,940 JPY).

Alternatively, if the Airport Limousine service serves your hotel directly, this is the most convenient service for those with baggage (avoiding changing trains at Tokyo Sta. or other JR stations).
The airport limousine site provides schedules, fares and hotel search services (roughly 90 min./ one way fare to central Tokyo 3,000 JPY).