Here's the conundrum - we usually have a lot to say, and people are forgetful. We end up repeating ourselves, and this usually takes away from the persuasiveness of the message.
Hence the need to focus on, and repeat, the MAIN idea of our message.
First - preview it, give background, explain "why"
Next, explain it - tell us "how"
Last - give us a recap and action steps.
This way, even the most distracted listener will have heard you, and hopefully, they'll "get it" too.