Here is an important piece of information that will really aid you in speaking powerfully. And it's so simple to use. For all your major points, do this: Make your point, give a descriptive example, and then remake the point as creatively as possible. That's PEP—Point, Example, Point. The PEP formula is designed to let you weave in examples and illustrations. Every major point you make needs to be supported to be memorable. You're taking advantage of how people learn (through repetition and illustration). Retention is the key to a powerful speech.
My training programs recognize the importance of retention, and I turn lessons into games and role-playing—vivid, real-life examples of principles that participants will remember far more readily than a dry synopsis. The same principle is at work in a speech; because people remember vivid stories and examples, use them to increase the level of what people remember when they listen to you.
After you have applied the PEP formula and have sorted out the various support materials, you may have material left over. If your leftovers won't group around your main points, they are probably irrelevant. Throw them out. Even if they do apply, set them aside, for they will probably make the speech too long. Make it a cardinal rule to stick to your main ideas, and get rid of the clutter. Sometimes these leftovers are handy if you ever need a longer version of your talk. I give 15-minute and 45-minute talks on the same subject and find the leftovers invaluable. But only if there's a proper place for them.
It's also possible you'll wind up with some important information that doesn't seem to fit under your main points. In this case your main points may not be broad enough. Go back to square one and restate them in a larger framework.