What Makes a Good Cover Letter?

Cover letter is simple, made sure to keep it formal and professional looking. Layout is in standard letter layout with personal information such as address, telephone number, email and name.
Include the date, name of person the letter is to, don’t simply put “dear sir/madam”, company name and address. Includes what the letter is for (ie job code or title). Finished formally and includes CV attached.  Make sure that it isn’t too dull and that some personality comes out in the letter, otherwise it will simply be overlooked due to it being too flat.
Simply laid out what the job is, why the person would be good for it and wants it, and why they are looking for a new job.

Make sure you only include relevant information, anything else will be in the cv anyway, don’t waffle on about things that aren’t important.
Also make sure the layout is correct and not poorly spaced, and that all spelling has been checked beforehand.

Don’t tell the employer what you want, tell them why they should want you. Be specific, but not annoyingly so. Tell them what you will bring to their company (or whatever) and how you can help them. Make yourself sound like a valuable resource that they need.
The cover letter is not designed to repeat what is on the cv, it’s to call attention to yourself, and separate yourself from other applicants.

Taylor a cover letter to the specific job, don’t write a generic one that covers everything.
Keep the cover letter short, you don’t want it being more than a page, and 200-250 words will suffice.