Let's discuss the verbal components of your speech. The oratory skills. Fairly, or unfairly, these will be the most closely associated to your credibility and your capabilities. So, understand the importance your voice has.
Above all, know this as a fundamental truth for all public speakers:
Speak monotone and you will lose your audience in less than a minute!
Oratory skills in public speaking is really all about vocal variety.
We can start with the rate, or the speed, of delivery. A comfortable listening rate for the average person is about 125 words per minute. There's a safe buffer margin of about 15 - 20 words per minute on either side. So, if you're delivering your speech between the parameters of 105 - 145 words per minute, your audience will nicely settle in. Anything below or above that rate and you're in trouble.
When the speech is moving too quickly, your audience will become frustrated as they will find it difficult to keep up to you. When the rate is moving too slowly, they become annoyed constantly waiting for the next word.
Of course it's completely acceptable, and recommended, to have moments when your speech is very fast and other moments when it is dreadfully slow. This helps to bring your speech to life and needs to be used as the exception and not the general rule.
Another important oratory skill is your pitch. Generally, a lower pitch is more welcoming than a higher pitch. Audiences find it difficult to endure a voice that is shrill. To those of you who may have naturally high voices, I'm not suggesting speaking in a lower tone that is not you. That would be inauthentic and prove to work against you. My encouragement is only to do your best not to allow your pitch to get higher during the exciting parts of your presentation.
A third area regarding the verbal skills is your vocal projection. This is about how loud or soft you speak. Is it appropriate to the room? To the subject? To the audience? Loud does not always mean better, still the group must be able to hear your entire presentation.
Pauses are the silent oratory skill, and all too many times overlooked as an important aspect of a presentation. Depending on where you incorporate a pause it can serve as an invisible exclamation mark, question mark, or period. It gives your audience time to catch up with what you're saying. It is also a tool you can use to formulate your next sentence while your listeners are contemplating what you just said. It serves a dual purpose when used skillfully.
Your voice must also be calm with an even timbre. It's the quality in which your voice is smooth and steady as opposed to shaky and choppy. This will serve to give you much credibility and add to your charisma. It denotes an air of confidence and leadership. The best way to accomplish this during the beginning of your career is by having your speech thoroughly rehearsed.
Speak softly in some areas, a little more loudly in others. Lower in some areas, higher in others. Slower in some areas, faster in others. During all this, speak in a confident manner.