Where is this letter going?
Speaking of headers on your resume and contact information you need to address your cover letter to someone.
Addressing your letter to “Whom it May Concern” or “Dear Madam/Sir” is tacky. Including a specific name is preferred.
It might take a little more time but researching the department name head or person most likely to see your letter is a great extra step. It not only shows that you care but that you are willing to do some footwork for the position. Even just addressing it to “XYZ Marketing team” or department is better than the old generic terms.
Your cover letter should be different for every position you apply for.
Take the time to write out a custom letter for each company. Spend a few minutes researching the company on the Internet. Read social media accounts for the company and learn what sort of culture they have.
Write about specifics with your cover letter that directly relate to the position and write in a tone that fits with the company.
Don’t rehash your resume.
Your cover letter should work with your resume. You want your cover letter to highlight different things from your resume. If your cover letter is the story of your work history or a narrative of your resume you are doing it wrong.
Resumes are meant to be short highlights while your cover letter can allow you to expand better on highlights that should be relevant to the position you are applying for.
This is also a place to show why you are a great candidate.