When writing a persuasive essay, it's important to incorporate the various elements of persuasion. You should be passionate about your topic and use your voice to convince readers to be on your side of the issue. Even if you are writing about something that you aren't passionate about (because it's for a class assignment) pretend you are and really put it into your voice. You should also try to appeal to your readers' emotions. If you are arguing about something controversial, tell an anectdote, putting an image in the readers' minds.
Make sure you have logical reasons to support your argument. Saying that someone should do or believe something because "it just makes sense" or "because everyone else believes it" is not valid and logical. You need to back up what you are saying with valid information and facts. On that note- use resources and definitely do not make up information.
Another thing to be aware of is that you do not want to threaten or bully your reader, and you don't want to let your own emotions get involved. Let common sense, logic, and your research to the persuading.