Before you begin drafting an argument paper, you need to do two things: pick an audience that might listen to you or should listen to you and decide what you will be arguing. The following prompts should help you focus your argument from a broad topic to a position on a narrow aspect of that topic.

What is your topic? (for example, single sex education)
What are three controversies associated with this topic? (for example, the constitutionality of single sex public schooling; the purpose of single sex schooling; the educational and experiential benefits of single sex schooling)
What are three questions people might ask about these controversies? (e.g., Is it constitutional for the public school system to fund a single sex institution? Can boys and girls receive a better education if they are schooled separated? Can sexism within education be alleviated through single sex schooling?) Which question are you most interested in exploring?
Now list several ways people might respond if you asked them your question. (e.g., Can boys and girls receive a better education if schooled separately? No, and besides it is legalized segregation. No, it does not prepare them to live together in the real world. Yes, studies have demonstrated the benefits of single sex schooling.)
Now decide where you stand in this range of responses. Think of a thesis that expresses your view. Write out your thesis and revise it until it is specific, has a stance, and makes one clear point. (e.g., Contrary to popular opinion and even well-meaning opposition, single sex schooling eliminates the devastating effects of sexism within the classroom and thus provides lasting benefits to young students.)