A cover letter should ALWAYS be included when the résumé is going through the mail – but never when you post to a job board or website (unless they specifically ask for a cover letter).
Try not to edit your résumé to fit the advertised opportunity as HR professionals are very concerned when a résumé is too much “on point,” instead, use the cover letter to address any special skills you want to emphasize or to cover topics that are not appropriate on a résumé.
In short, don’t tinker with the résumé and its OK to tinker with the cover letter.
Don’t write a very long cover letter, as a long cover letter can kill your chances of getting your résumé read. A great cover letter is 3/4/5 paragraphs long and on a single page.
