You look around the room and you notice that some of your audience are looking at their phone, watch, the ceiling – anywhere but being focused on you - the speaker! Try a few different approaches to get people’s attention back on you.

Walk around the room or stage. If you are unpredictable the audience will keep their eyes on you to see what you do.
Pause when speaking and use inflection in your voice. There is nothing more sleep inducing than a boring monotone presenter so raise and lower your voice and use inflection to drive your point home.
Speak faster or slower. When you change speeds, people take note: Moving from a slow vocal delivery to a fast, punchy one will keep people focused on your speech. Works well when slowly describing a problem and then deliberately increasing speed to a punchy delivery of the solution.
Storytelling. Relate the topic of your presentation to a real world example as this will help the audience to understand it’s application.