I am not really good at speeches but if you are, then these are some tips to making a good speech.
1) Try to convince others that being a class counciller doesn't mean a very high rank but you are the same as others, but being one tell others that you will do the littlest bit to make a good counciller.
2) If you are a charismatic person, try to get your friends to help you out, in speech, or just in voting. If you are popular even better.
3) Understand if you were going to be voting to a class counciller, what would you like to hear?
4) Try to be funny, or casual, or something different than just being some serious student. I would vote someone funny definitely.
Yeah thats all I know. I hope it helped.