It is first important to understand what the essay question/statement is asking of you. Unpick the question or statement, and then set out your argument.
Outline your opinion at the start of the essay. Doing this will provide you with a clear and sound starting point to base your argument.
Think about the reader: who are they, what’s important to them, what are they expecting?
Your writing is likely to be better if you have a good process, which moves you from gathering your ideas, to organising them, to presenting them to your reader. Remember to look at the evidence (research) you’ve gathered and construct your argument based on your reading and analysis
The more conscious you are about why you are doing a particular bit of writing, the better that writing is likely to be. Think about a theme to thread your argument together. In a persuasive essay, you will relate each paragraph back to your opinion and argument.