Your delegates need to be able to see and hear clearly.
Screens need to be big enough and raised from floor level so that people can see.
For larger audiences your speakers will need microphones (preferably tie clip) and proper amplification. This is especially important if there are likely to be any language difficulties.
People's ability to receive information is directly proportional to the comfort of their seating. Seating should be comfortable and well organised.
If people need to take notes or work with papers then classroom style or casino style seating at tables is recommended. If using casino style seating, use only two thirds of each table to avoid anyone having to sit with their back to the stage.