When I was in school,I used to take part in all  the activities which involved any kind of public speaking ,for instance-Debate,Speech or hosting any show.And believe me,I used to enjoy it a lot as by this people get to know about  myt houghts,mindset,and the way I feel about a specific subject.
By speaking in front of hundreds of people,you gain lots of confidence coupled with a great medium to present your views and in return get the response hand by hand.
But,an effective speech involves a regular eye for the matter with guts to speak out your mind and handle the pressure of questions pouring your way by one or the other person.
I can even share few important facts through my personal experience 

  ** What I have learned from my experiences is that if you really want the public to listen to you calmly without creating any mess in between, your speech should concern the public sitting in front of you.They will show interest in you only when the subject has something to do with them too and can effect their lives in one or the other way.

** Also,in between the speech,you should add some real life experiences so as to make them believe that what you are saying is not a fairy tale instead is very much related to the practical life.

** People show their interests if you keep on entertaining them with good jokes and funny incidents.Thus always try to include it in your speech.

** Good speakers are not born,they are made.TRUE.If you ever feel discouraged or are scared of speaking your mind,just practice prior to your turn and never let your ideas go with the wind,that means,donot change your  mind because the person listening to you doesnot like your way of thinking and therefore is not at all interested in giving a ear to your talks.

** Always try to convince the people that your thinking is not related to your benefit only,but you are more concerned about them.And this can be done by regularly asking them some questions in between and pressurizing the need of the change for their own goodselves.

** At the end,be courageous enough to face the critics’ points, as they are the ones who actually affects the person’s view on a particular subject.If they donot like the points suggested by you,give them alternatives or prove them that what your are saying is beneficial for the entire group of people involved.

So guys,If you really think you have the capacity to take the public in confidence and make them believe in you,what are you waiting for?Go grab the opportunity and change the way the world looks !