The best public speakers know how to engage an audience. There are different ways to achieve this.  I break them down into three categories.

People came to here you speak with expectations. They’re expecting to hear your thoughts and ideas with the hopes that they’ll uncover something useful to them, their job and their company.

Ideas – Bring something new to the table. Research information
that the audience may not already know. Draw unique conclusions that
are important to the audience (and tell them explicitly why they’re important).

Why
At the end of the day, the conclusions are what matter. They’re the reason people came. Make sure the ideas you present are new, interesting and relevant to the audience.

Variety – Don’t use the same method of communication (talking) throughout the entire presentation.

Incorporate   
– videos and images
– different colors
– audio clips
– white boards

Why 

– Not everyone learns the same way.
– Outside sources can reinforce your points through added credibility.
– People’s eyes and minds have to refocus when the method of communication changes.

Interaction – Ask the audience to do, or say, something.

Examples
– Ask for questions at the end of the presentation.
– Have the audience do an activity (i.e.  Personal introductions if it’s a small group)
– Ask for volunteers for a demonstration.

Why    
– The audience has ideas too. Let them contribute.
– Also, if the audience doesn’t know each other and it’s a small group,  (15 or less people) introductions can ease any unnecessary tension.