Format
Avoid email. Anyone who has their email address published online is the target of oodles of spam. Elected officials have their email addresses published on multiple websites, including this one. They get lots of bogus email messages. This makes it very easy for them to neglect legitmate but unwanted messages from constituents, activists or advocates.

The medium is at least a big part of the message. An old-fashioned paper letter, sealed in an envelope and sent by Canada Post will be much more likely to get the attention of the elected official. The mere fact that the writer went to the trouble and expense of posting a letter will carry weight that an email cannot.

If you've got good handwriting and you're not sending dozens of letters, a handwritten letter can be more effective than a typed and printed letter. If your handwriting is not very easy to read, opt for the more legible printed message.

When writing to county councillors, send a copy to the County Clerk. Mark this copy:
"To the Mayor and Council:
Attention: County Clerk
Please place this correspondence on Council's next agenda."

Content
Get right to the point. Let them know exactly what you are writing about in the first sentence. Give them the gist of your letter in the first paragraph. Limit your letter to one topic. Short and sweet is good. Often, your letter will be screened by an assistant. If they are receiving a lot of letters on one topic, they will sort them into pros and cons. When an elected official sees a large stack of letters opposing a nuclear plant and few in favour, they will be thinking about electoral ramifications.

Ask a question. Rather than simply making a statement, elicit action and a response by asking a question. This should be a "real" question as opposed to a rhetorical question. A realistic question might be something like, "Will Council take the necessary action to prevent the construction of a nuclear power plant in Nanticoke by passing a resolution declaring the county to be an unwilling host community?" A rhetorical question might be something like, "What good are jobs if we don't have our health?"

Be respectful. Despite the common perception, most politicians and elected officials really do want to serve their community. For the most part, they could earn higher salaries in the private sector and few local politicians aspire to higher office. They work hard and listen to lots of complaints. Don't be timid about giving a pat on the back when you feel it is deserved. Most politicians deserve more praise than they get and flattery can get you somewhere. 

For local politicians like county councillors, making a decision on whether or not to allow a nuclear plant in their community is a huge responsibility. It's one that they'd just as soon were not in their laps... but it is in their laps and they must do their democratic duty and represent their constituents. Be firm and forceful about expressing your objections but have a little sympathy for the awesome responsibility with which these public servants have been saddled. 

Use word processing software with spell check and grammar check. Even if you're going to send a hand written letter, it's advisable to compose your letter in a program like MS Word or Word Perfect.

Read your draft aloud before committing it to the final version. If it is easy to read and understand when you read it aloud, it will be easy for the recipient to read and understand when they see it for the first time. You will probably write and rewrite a few times. You are very familiar with your topic and viewpoint. The recipient will likely just read the letter once. You've got one chance to make your point. Don't assume they will know what you're trying to say just because you know it so well and feel so strongly about it.

Format
Letters to the editor are somewhat easier than letters to elected officials. The biggest difference is the acceptability of email. Papers do not place a higher importance on printed or handwritten letters. In fact, emailed letters are easier for them to deal with. Handwritten or printed letters require transcription for publication. Emailed messages can be copied and pasted into the newspaper's editing software.

Content
Brevity is desirable. Try to keep your letters under 300 words - under 200 is even better. Some papers, notably the Port Dover Maple Leaf and the Regional News, will often publish longer letters. The Simcoe Reformer, Dunnville Chronicle, Brantford Expositor and Hamilton Spectator prefer shorter letters. While they may edit long letters, they are more likely to just leave them unpublished. Editing letters, like transcribing paper letters, takes work and most papers are struggling and short of staff.

If possible, write your letter as a reaction to an article or editorial that you read in the paper. Cite the headline and the date the article appeared. You can send the same letter to multiple papers but if you're citing and responding to an article that was published in more than one paper, make sure you adapt each version to the specific publication. Many papers carry the exact same articles with different headlines.

Avoid accusations of anything that could be construed as slander or libel. Newspapers will reject anything that might result in legal action. Even though you are the author, they are the publisher and they are legally liable for whet they print.

Include your address and phone number. This is for legal reasons. You can mark the address and phone number as "not for publication" but you should include this information. Some papers will call you to make sure it was actually you who wrote the letter that will be published bearing your name.