A letter to the editor needs to begin with the presentation of the subject and the article the writer refers to. Then, the writer has to state his/her argument, show what he/she wants to say about the subject and state his/her position, what he/she thinks about the subject. After that, he/she has to prove what he/she say by evidence (numbers, examples, etc). At the end, he/she has to say what people can do to change things.
The writer has to use a formal tone and be original, he/she musn’t use slang or says something has already said.