How can you know what your audience wants?

The worst thing you can do is: not be interesting, not bring anything new, not be surprising, not be funny, not be moving. Prepare thoroughly. The mistakes you can make during a speech are far less important than the mistakes you can make beforehand. Make as much as you can beforehand. There is no such thing as too much preparation, there is only the wrong kind of preparation. Prepare, practice, conquer.