Keep walking, turning and looking audience in the face - select a few people randomly for this. This will force audience to follow you around and reduces boredom.
Use the full stage for your talk. Dont just stand at one place. Standing just on the podium is the worst thing to do.
Try to vary your voice to suit the phases of the talk. Dont make it sound like a boring lecture at the same pitch and tone. It tends to put people off and in worst case to sleep. Use variations of pitch and tone to your advantage.
Dont use elaborate 10 min + introductions. People dont have that kind of patience these days. Dont forget that your talk is judged in first 10-15 mins in this age of twitter.
Structure the presentation so you give interaction options in between the talk rather than at the very end. This puts audience on their toes and makes it more interesting. Keep it as a conversation (dialogue) than a monologue.
I have often found this is one of the best ways to engage the audience - to add a light touch of humor where it fits. Everyone reacts to a good laugh.
Pictures speak more than a 1000words. Slides with just text are BORING. Use graphics/video to good effect. Theme your presentation. Also reduce the amount of text per slide - not more than 4-5 lines at worst case.
Wherever possible, try to give real life analogies rather than pedantic examples.
Courtesy : Anand B. Pillai