You may refer to notes but avoid reading long passages to your audience. This means periods during which there is loss of eye contact and therefore loss of interest. Look around the room frequently to keep connecting eye to eye with individuals in the room. Your audience will soon be aware that you are alert to them and pay more attention. They are also establishing a relationship with you whenever you look directly at them, and are more likely to ask questions or take part in discussions.
Eye contact is feedback as well.
If you find more than one individual with a puzzled face, it means your audience is confused. Go back and paraphrase what you have just said. Restate your thoughts in different ways to help your audience understand you better. When you find your audience looking everywhere but at you, you have lost them. Try to re-engage them with a floor discussion or question and answer session, a pause, a change of tone or topic.