Cover letters are introduction documents that are written and attached together with other documents. A cover letter is the first contact the receiver has with you. Therefore no effort should be spared to ensure that it is done well. Most of the times cover letters accompany resume, curriculum vitae or business documents.>
Basically a cover letter should be simple and straight forward. It should not be more than a page long and 2 to 3 short but succinct paragraphs. By reading your cover letter the reader should be drawn to read the attached document(s). The cover letter should not be a repetition of what is in the attached documents but should give the reader a glimpse of what to expect. There are different cover letters written for different purposes.
You should not use the same cover letter to apply for different jobs for instance. Before you embark on crafting a cover letter take your time and get all the necessarily background information. Know about the organization or the reader you are sending the cover letter to. Research how to write good cover letters. Find different cover letter samples and work your cover letter around those samples.
A well written, highly targeted cover letter greatly increases your chances of getting what you want. It could be a job interview, a business deal, etc. Therefore take your time to research and write a good cover letter. You will thank yourself you did.