Before taking on a crowd and telling them something, convince yourself first. You yourself perhaps are the most difficult person to convince and once you can get that done, you are on the right track. Be motivated and believe in what you are about to tell others. With pure belief, you can turn the tides, getting a crowd hyped up may not be that hard.
Whichever topic or issue you will speak about, make sure that you are well prepared in it and have done all your homework. If someone has a question, you must have an answer. Adding a bit of wit to tough queries will spice it up further.
You will get moments when you may feel that the crowd is taking over and you are losing your grip as someone will always pass nonsense comments which you will annoy you. It is natural but be sure to not lose your calm. This is important because if the crowd feels that you are getting irritated and side tracked by nonsense, be sure more will be on your way.
Seize the Moment
There is a moment in every speech where you gain the utmost attention of the crowd. That is your time to steal the thunder. Once the crowd is hooked, you must keep them that way. Do not let go of them and make sure they simply cannot do anything else but listen to you. You will also get the feel of what the crowd appreciates more, keep that in perspective and move forward.