Escribir un corto discurso (si quieres en inglés) sobre como escribir un discurso?

First you have to know what do you want to achieve with your speech.

After that, put it a striking name, third one, be ready with the conclusion, that people who are listening have a reflexion about what did you say.

Have in an order your ideas, in a logic one, have good arguments to be convincing ; the introduction has to be intresting to present the speech just like in the past step.

Try and try to memorize all the speech, the important ideas an arguments.

And finally, write it.