I'm reminded of the days I managed grassroots campaigns for corporate 500 companies and national trade associations across the country and we followed some pretty simple but effective rules.
First and foremost, the legislator's name and how you want the legislator to vote on the specific issue you're addressing must be in the first paragraph without fail.
Those two things in the first paragraph will get the attention of their staff and in turn it will end up on his/her desk to read, if your letter is published.
Second paragraph should talk about the issue in detail. This is a great time to state the facts and any other information you want out in the public domain.
Close with the action item - vote for or against a piece of legislation. Again, this is key!
It's also important to put your full name and full contact information on this communication. That's what makes it legit and hopefully published from the papers point of view! And don't be surprised if you receive a phone call from the paper before they publish your letter-to-the-editor.
Your goal is to get your legislator to support your position. Don't let them off the hook and with the typical "I'll keep your views in mind" should this legislation come up for a vote response, if and when they reach out to you in response to your letter.
Remember, in the grassroots business, you're in the business of influencing a legislator to vote a certain way. Once you've secured that vote, you move on to the next legislator (most campaigns are targeting multiple legislators at the same time). That's how the successful grassroots campaigns are run.
While these are basic suggestions, it will give you a better chance of getting that letter-to-the-editor published.
And isn't that your ultimate goal?