Emmy
Hey Emmy,
When you're doing a speech, the most important thing is to have a theme or an object of interest. When you have a theme and/or object of interest, you not only engage the audience from the get go but you can refer back to it right at the end of the speech which makes it memorable and super interesting. For example, if you take a look on the internet, I saw one with a Rubix cube. Maybe a chess piece, a boat, your school logo, a pencil, a piece of paper. And then at the end, refer back to it and it leaves a lasting impact on the audience.
In terms of humour, you don't want to overdo it; just sprinkle maybe around 3 in the whole speech and if you want, just search up a few jokes. Also, don't force it into the speech, ensure it flows well with the rest.
Hope that helps. Feel free to ask any more questions.