It's interesting to note that only a generation or so ago the topic in the title of this article would probably never have been discussed in a high school social studies situation. In some countries two generations ago certain behaviour between people of the same sex was deemed to be against the law. In creating your argumentative essay, you might care to mention recent history as regards same-sex marriage. It would make an interesting introduction to the topic.
But despite the fact that the subject is of interest in terms of social history and how society has changed in its attitude to certain lifestyles, you are still composing an argumentative essay. That means that you need to have a thesis statement which is the main point of your argument and from there the rest of the essay will be used to support your argument. You will of course gain extra points if you are able to comment upon the counter argument as well.
The basis of any argumentative essay is that there are at least two points of view or two sides to an argument. You have to clearly state the argumentative point and include your stance. Which side of the fence are you on? Then, through reason and writing and showing the benefit of your research into the subject, you argue your case. It is most important that you do not use emotional language. This is a subject for discussion and one which divides opinion. You have your opinion and in your essay you must justify it.
Remember the counter-argument situation as mentioned above. There will be an alternative point of view to the one you have argued for. What is this alternative point of view and how are you able to dismiss it?
It is often said that you should choose an essay topic in which you have an interest or some previous experience. It’s not essential but it can certainly help. In the same-sex marriage essay, you would be wise to select a point of view in which you believe. But you should beware of using any form of prejudice in your writing. The issue is the issue and your belief system, though important, is not the point here.
Reasoned argument with points to substantiate your point of view is what will help you write well and be rewarded accordingly.