its always better to stand in front of mirrors to practice as we have a audience in the mirror so you will have confidence.breath deeply and so that the stress will reduce to minimum....

Start bulding confidence in you. belive that you can speak in front of thousends of people without fear. don't bother about success or defeat when standing in front of people. just stand and speak out your mind.
just before going to stage in dressing room or so shout loudly as you can. shout as if you are lion (in yoga its called sinha mudra)
after 2 / 3 min. close your eyes take few deep long breaths and then go to stage.
on stage look directly streaght into audience eyes. drop all your conclussions about crowd. be natural and you will see that you are profound speaker.
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Love Moves the world.

I also used to participate in debates and declamation contests. I used to do rehearsal in front of the mirror or I shall invite some of my seniors in front of me to remove my stage fear. You can also do that way. It is very helpful.