The short opinion pieces you are asked to write in the semester should ideally be publishable. In other words you are giving a go at quality writing for an educated, broad readership as one would in a good newspaper, magazine or professional blog.
Researching what you write about is necessary!
When you write to be published, unless you want to be branded as an idiot for the rest of your career, you do not make bold statements about anything without doing some basic fact-checking (in-depth fact-checking is even better). If you are unsure about what you say and your research does not provide any backing, find something else to write about!
Making use of what you read in order to write your opinion piece
A good article is generally one by the writing of which you learn or deepen your knowledge of a particular topic. Your argumentative line reflects the new perspective your writing has brought to you. In other words good writers are not people who have some preexisting knowledge and pour it into their articles but rather people who acquire knowledge and sharpen their critical vision of the world through writing.
You should therefore use what you read both as a source of information and as a resource to deepen and sharpen your own worldview. This is a creative process that often takes place in the process of writing: writing enables you to clarify your own thoughts while handling a wealth of information, and this clarification leads to revisiting what you have just written. Writing may therefore be something that is done in several stages: a first draft may lead to a second which may in turn lead to a third. Not everybody works in this way; some people construct their articles without putting anything on paper and when they start writing they know exactly where they are going. But whatever the way one goes about writing, one thing is true of all: once the piece is finished, one should feel that one has acquired more knowledge, on the one hand, and that one has clarified, deepened and sharpened one’s own thoughts about a particular topic, on the other hand.
You must catch the attention of readers right from the beginning of your piece!
Very often a reader will decide to read something because they find the title attractive. They will expect the whole piece, including the first paragraph, to be what the title says the article is. Therefore an article that does not immediately start with the heart of the matter will not be read: many readers won’t go further than the first couple of lines. Choosing a telling, catchy title and a thought-provoking or punchy opening sentence is therefore very important.
Giving a title to an article
Press articles and blog entries usually have titles in the form of a sentence that represents the main point of the piece. Whenever possible English-speakers will try to make a pun in the title, for example playing on a famous quote, saying, proverb, etc (this is also the case for books: publishers love titles that contain a pun or have a comic touch). Making puns is difficult and one should focus first and foremost on a title that truly represents the point that one makes in one’s piece of writing.
The best way to learn how to write titles in English is to observe what journalists and bloggers do.
Do not multiply your argumentative lines!
A short opinion paper generally makes one particular point and relies on one argumentative line that is presented in enough depth to leave the reader with something to chew on. If you want to raise too many questions, you will end up not making any impression whatsoever on the reader.
Writing for a broad readership
You are writing a publishable piece that must be readable by people who have not attended the class at Paris 8 or read the documents you were given. When referring to them or their authors, you must therefore introduce them in a few words. You should also write sensitively; while making your opinion crystal clear, you should refrain from inflammatory comments that may offend potential readers.
The use of footnotes
Footnotes are used extensively in academic writing, a lot less if at all in the press or news blogs. Although there is nothing wrong per se with footnotes in a short opinion piece, it is unusual and it would be good for you to learn how to stylishly insert references to a particular book, article, paper, etc, in the flow of your sentences. In any case these references must appear.