There's no correlation between the length of a talk and its impact. 

Have a good beginning, a strong ending, and put the two as close together as possible.

Any communication that you are willing to pay for begins effectively. 

Your job at the beginning of a talk is to capture attention and convince your audience that it's in their interest to listen. All's well that begins well.

Listeners cycle in and out of attentiveness--mostly out. Twenty percent of your audience will be spaced out at any given time.

So when you begin, establish your themes, and as you move through each section remind them where they are on the journey. When you get to the end, repeat your key points.

Attention-getting messages are simple, unexpected, and concrete.

The mention of an object creates a visualized idea in our minds--we form an image of the thing, and retain it in our memory. This doesn't happen at the mention of abstractions, like "value" or "memory."

Rehearse. An audience doesn't want to see you struggling to say what's on your mind. 

They've come for a show, an organized presentation of thought. Know your lines: your opening line, headlines, bottom line, and story lines. Being prepared will help you come across in a conversational manner, too.

Know how to stand (either behind the lectern, where you're half-hidden but feel safer, or out on the open stage) and move in such a way that you communicate the intangibles that motivate others to believe in you. Body language was the first language.

Also, know how to project your voice effectively.

When you're speaking, if you're having a good time, inform your face. Your face is the most valuable real estate in any meeting room.

The audience wants to hear, see, and sense your face enjoying your belief in your clear and simple message. When they do, you and your ideas will be more convincing.

Good content may be necessary for a successful presentation, but it isn't sufficient: it doesn't guarantee success.

You must frame your good content so it holds attention and show up on time, dressed to say what you have to say in a lively, engaging manner.