Question

how do you write a persuasive speech?

Answer 1

Play to your audience...always.
carefully define what it is you want to persuade that audience to do. It is difficult to get where you are going if you don't know where that is.
Pick a number of reasons based on time allowed - a 60 second commercial will have fewer reasons than a 30 min infomercial
rank those reasons in order of quality
Then decide if you want to start with your best stuff first or best stuff last --- just don't put your best stuff in the middle
There your speech is pretty much written

Answer 2

persuasive is powerful, influential, effective. Meaning, you have to provide a strong words that you may use on your speech. Be concise, to obtain excellency in public speaking.