Include quotes from your recommendation letters.I always advise against putting the tired line, "recommendations available upon request." After all, if the employer is interested he'll get in contact with you, and resume real-estate is too valuable to waste listing throwaway lines. However, if you have a strong letter and can include a quote right in the text of the cover letter it could add to both the content and authenticity of your letter.
Include a list of what you could do for the employer.This obviously requires a fair amount of research, but if you can identify certain needs or weaknesses of the company your are applying to detail exactly how you could help them remedy the situation. This does two things for your candidacy. First, it shows you have initiative. Second, it gives them a frame, or brand, from which to view your resume. You will have predisposed them to read your history as one that can solve their problems.
Keep it short and to the point.A common mistake I see, both from job seekers and professional resume writers, is going on too long in the cover letter. You do not need a 5-paragraph essay or a white paper. The purpose of the cover letter is to get the employer to read your resume. Let them know the job you want and why you'd be good at it. Tease them with a few quotes or facts about your history and preemptively thank them for the chance to speak in person. That is it.
Use these three tips to better your chances and get your cover letter read, which of course leads to the resume and interview and hopefully a new job.