Decide on the topic and paper. Your letter to the editor can be a response to a number of things. Most likely, it will be a response to a specific article, but your letter could also be a response to an event or issue in your community.
It’s best to respond to a particular article that was published by the newspaper. Then, your letter will be more likely to be chosen for publication.
If you are responding to a community event or issue, your local newspaper is likely to be the most appropriate venue for your letter to the editor.