One of the things that most people pay no attention to when giving building their presentationis the concept of control: perhaps better said as "Management of the (Audience's) Mind"

All presentations are created with an objective: persuade, educate or inform.  If we ignore the idea of control in a presentation, then it's a fair bet that an objective is not going to be achieved.  People's minds wander or they go to really would like to know how the researchers discovered that (very neat) statistic.  (ALWAYS beware of statistics that fit a comfortable number...10%, 25%, etc.)

How then do we maintain control during a presentation?  We do this by making sure that the only things that they can focus on what we want them to focus upon.  This means ensuring that that the subject matter on the slide is relevant to the point you wish to make.  The classic error of too much text is one area that allows the audiences mind to wander off.

Essentially, it requires that you be clear about the objective of every slide.  The traditional 6 points per slide, 6 wprds per point is wrong by a factor of 6!  Limit each slide to one point only.  If it is important to see all the points together, create a slide at the end of the points that includes all the points on that one slide AFTER you have dicussed each point.

When you can manage the audience's attention you will have more chanc of leading them to your desired outcome.

Cheers!