Adress Somebody Specific or nobody
If you’re unsure of exactly who will be reading your cover letter, don’t address it to “whom it may concern”. It looks like you haven’t done your research.
As with wit, cover letters require brevity. Boring them with an inefficiently written letter, especially in your first contact, isn’t a good idea.
Write about the company
Show that you’ve done your research. It demonstrates your seriousness about the job, and a proactive attitude.
There’s a very good chance that sending a pages document, or even a word document, will result in formatting issues. PDF your document before sending it over.
Name drop a mutual contact
In your first sentence, grab their attention by mentioning a mutual contact. Make sure that your recipient and the mutual contact are on good terms first. A recently fired employee isn’t a good contact to mention.
DO NOT DUPLICATE YOUR RESUME
Don’t hit the same topics as your resume. Nobody likes to read the same thing twice.
Tell a story
If at all possible, give a bit of a narrative. Narrative’s are more memorable and moving.
Finish by saying how and when you’ll get in touch
A good way to again demonstrate your proactivity, and make for more efficient communication is to finish by saying how and when you’ll get in touch.
Highlight your Work Related accomplishments
Go over your work related accomplishments in your cover letter. They’re too important to wait for the next page.
If unsure, go formal
Many people like to add a bit of personality into their communications by being casual. This can be endearing, but be absolutely sure that it will be received well. If you have any doubt, go formal!