They see and they remember.
They do and they learn."
It may be difficult to define what the good presentation is. But almost people who have experienced could remember which presentation was good or bad.
Well, let's go back to the first presentation! Even though each one has each problem, the same thing everyone agrees is what we have always forgotten is what we have already known.
Now, it is time to move on your good presentation with the first step, audience involvement.