Once you have chosen a topic and you have chosen a perspective to analyze the topic from, you can begin to write your paper. Good ethics paper state facts. They also avoid equivocating ethical with lawful. There is a distinction between it being wrong to kill someone and it being illegal to kill someone. Consider the following example: Chris broke the law when he ran the red light. Chris is a terrible person for running the red light. We might agree with one but not two. Good ethics papers also argue from one of the main standpoints in ethics - but they also consider the other two. For example, if you are making an argument to assist the suffering from a Kantian perspective, you must also address what the virtue ethicist might say and what a utilitarian might say. Then, you need to show why the Kantian perspective is better.
Finally, don't forget to outline and then revise your work. The best papers are those that are well-organized and well written with very few spelling or grammar errors.