What makes a person a convincing public speaker?

Personally, I wouldn’t know. I’ve never had to give a grand speech. Here are a link on the subject, though.

http://www.ehow.com/how-to_4845368_deliver-effective-speeches.html

At first I wanted to say “Oh, well, for me it is if they speak with confidence and show no signs of nervousness” and, well, that still does apply, but the situation you’ve given makes it a little different, I believe.

An audience sharing the view does help though. They just have to be slightly towards that direction and all they need is a good speaker to push them straight into it. Others, well, I think it may have to do with them hearing what they WANT to hear. Even if that want is subconscious. We are emotional creatures and sometimes, our feelings override our logic..

But anyway, that is just my current opinion. I probably don’t know anything :P

u need to make eye contact in order to be assertive, speak like you know what you are talking about to get the facts out, even if its just bullshit. makes you seem prepared. use hang gestures, makes it look less awkward, those are great things to do when u are trying to be persuasive. i didnt read the more part of ur question so idk if this answers anything, lol

It is not what you say, but how you say it. Someone who is assertive, charismatic, and bold talking rubbish will be believed before someone who lacks self-confidence but is reciting fact. It is absolutely not limited to religious spheres. Politicians do it ALL the time. Check out Fox News, e.g.

First of all, marshal your facts and plan your content. Then take notes only big enough to fit on a 3×5 index card. Have a command of English usage and syntax; speak clearly, stand tall, pretend you are having fun.

Soon you will; politicians who are bombastic or fustian generally get found out, charisma or not.

Having people who share your views, good posture and voice projection is all good. Really.
But what really convinces people is what the topic is, the emotion behind the words, and the words themselves. Example:
Hitler put so much emotion into his speeches that he rallied the German people into war. (Plus Germanic languages give an ‘umpf’ to it. Something like Chinese is almost a detrimental item.)
The topic:Obama was calm through his speeches, yet the topic was so wanted, that anyone who listened was convinced he was right. People wanted someone new. (They also wanted a better economy.)
The words: even if it isn’t smart, you can still sound smart. I win my arguments doing this. I pull a whole lot of crap out of no where, but it sounds right. (Its like the joke: 77% of statistics are made up.)
And charisma helps too. I don’t care if you like him or not (really, I don’t care, so don’t comment), but Pope John Paul II was liked by so many people, that he (along with Ronald Reagan) tore down the Iron Curtain and led nations against communism.

Odds are good that the “rubbish content” is perfectly valid in the proper context. I’ve never heard of Louis until now, and I am unfamiliar with the context of the quote. But ten seconds’ research seems to indicate that Giglio operates “inside” the Church (as it were), in a setting that already provides certain foundations and frameworks that don’t exist “outside”. The quote’s generator was probably not entirely aware as so many are not of the role of context in the situation, and attempted to relay one of Giglio’s exceptionally good points without it.
Imagine a baseball fan going on and on about his favorite team and players, and his audience is a person who’s never even heard of baseball. The facts are true and the figures too, but they mean nothing to, say, the Pygmies in Africa.

Experience in public speaking, giving presentation, facilitating workshops and discussions. Just do it again and again and you will get better. Start with small groups and people you know.

Thanks to everyone who has answered. I find the power of speeches interesting, as it seems a well constructed and well presented speech can move a crowd into a state where they will do anything.

@Nullo You are right in that his work is largely aimed at people inside the church, but his reasoning is woeful regardless of his intent. It would be remiss of me to speak of evil spirits causing disease whether I was talking to tribesmen in PNG or giving a Nobel lecture. The intent is not so relevant any more when you consider exactly what he has said.

In the case of BHO, it is a teleprompter.

@FireMadeFlesh
I cannot comment any further on the matter, as I am unfamiliar with the man’s work, except to say that a different perceptual framework isn’t necessarily a bad thing.