Presenting to an audience is no different than having a one on one conversation with someone. You can read the signals. When are people surprised, amused, intrigued, bored, confused? Pick up the non-verbal feedback and try to adjust.
You will be in for some surprises. I have been surprised many times. Slides that I thought were funny, were not. Points I thought were clear, were in fact confusing. Stories that I thought were somewhat dull (and I was considering cutting them), got people interested.
If the lighting in the room is poor, the people in first-row will probably end up being your focus group.