The best way I usually go about starting persuasive essays is with a question/answer type setup.
Usually, based on whatever your topic is about, make the VERY first sentence be a very important question that has to do with what your essay is about. Then, answer your own question.
Throughout the essay, you can either provide evidence to back up your reasoning or keep making new points and backing up THOSE with evidence. Just make sure you have a strong thesis that covers EVERYTHING your essay will be about. You can go back and edit it later if you must, but a strong thesis is sure to score you some points.
For the conclusion, make sure it restates your thesis. Don't say something like: "Well, from all of these examples, you can see my point."
INSTEAD, restate your main topic sentence, and then take whatever evidence you had in each of your body paragraphs and summarize it into your conclusion.
~Hope this helps!
