If you want to write an effective letter, follow standard letter writing conventions and write in a clear and assertive style, using action verbs and avoiding passive voice if possible. Addressing a person properly, making sure your grammar and spelling are correct, and assuming the proper tone will all help you to write an effective letter.
Follow the proper letter format. In the upper right hand corner of the page, put your name and address. You can also include your phone number and/or email address if you want to. Leave a double space and then add the date.
Choose the right salutation. "Dear" works for most types of letters, formal and informal. The business world is more casual than it used to be, and if you're already in the habit of addressing the other person by their first name, then use their first name in the letter to keep the tone friendly. If you're unsure how they expect to be addressed, use their title and their full name.
To write an effective letter, you must lay out the content in a logical format, with paragraph breaks for new thoughts. Use action verbs as much as possble to make the letter more interesting. Keep your paragraphs as short as possible and use block style paragraphs with a double space between paragraphs. White space helps the eyes stay relaxed while reading.
In the tone of your letter, keep the right emotional distance from the person you are writing to. If you are writing a letter to someone you are close to, be warm and casual in the letter. If you are more formal in the letter than you are face to face with that person, they might take it as coldness. If you are too informal in a business letter, however, the recipient might interpret that as lack of respect. Even in an informal, non-business letter, being too friendly to someone you hardly know might freak them out.
Leave only one space between sentences. It is sometimes acceptable to leave two spaces, but this is generally considered an obsolete convention. For other details of style, consult a style guide. Writing in correct and modern style is not essential for an informal letter, but it is important if you want to come across as professional.
If you are writing a formal letter, clearly state the purpose of the letter as early in the first paragraph as possible. Follow up with any related details and make it clear if you are expecting a response, and if so, what kind of response. To write an effective letter you must be assertive without being pushy.
Use action verbs and avoid the passive voice, which makes sentences vague, weak and uninteresting. For example, instead of writing: "The dog was walked," write, "The woman walked her dog." Instead of "I was told," write, "He told me."
Use small words instead of big ones whenever possible. Big words include not only uncommon or academic words, but also common words with many syllables. People tend to zone out when they encounter too many long words, especially when there are a lot of them all clumped together.
If you want to write an effective letter, use contractions whenever possible. For example, use "it's" instead of "it is" and "there's" instead of "there is." It's easy to fall into the habit of not using contractions when you write, but that tends to make writing seem stiff and dull.
End with a short, friendly paragraph to wrap up the letter. In an informal letter, you might want to ask some questions about how the other person is doing or what they've been up to. In a more formal letter, if you're expecting a response, you can reinforce that expectation by writing something like, "I look forward to your response."
Close the letter with an appropriate closing. For a business letter, "Sincerely" is a good choice. For a friendly letter, you can use "Love" if appropriate, or "Warmly," "Fondly," "Regards," or just skip the closing. Leave four spaces after the closing and then type your full name. Sign your name above the typed name. For any kind of letter it's a good idea to sign it by hand. If you take a moment to give it that personal touch it will create a warmer feeling in the person who receives it.
Polish your letter. Check spelling and grammar carefully. Look out for homophones (words that sound alike but are spelled differently). See the Resources section for a link to an article on how to avoid common grammar mistakes.